diff --git a/autoload/ale/linter.vim b/autoload/ale/linter.vim
index c791ba4..5eb2fd8 100644
--- a/autoload/ale/linter.vim
+++ b/autoload/ale/linter.vim
@@ -227,6 +227,21 @@ function! ale#linter#PreProcess(linter) abort
                 throw '`completion_filter` must be a callback'
             endif
         endif
+
+        if has_key(a:linter, 'initialization_options_callback')
+            if has_key(a:linter, 'initialization_options')
+                throw 'Only one of `initialization_options` or '
+                \   . '`initialization_options_callback` should be set'
+            endif
+
+            let l:obj.initialization_options_callback = a:linter.initialization_options_callback
+
+            if !s:IsCallback(l:obj.initialization_options_callback)
+                throw '`initialization_options_callback` must be a callback if defined'
+            endif
+        elseif has_key(a:linter, 'initialization_options')
+            let l:obj.initialization_options = a:linter.initialization_options
+        endif
     endif
 
     let l:obj.output_stream = get(a:linter, 'output_stream', 'stdout')
@@ -451,12 +466,20 @@ function! ale#linter#StartLSP(buffer, linter, callback) abort
         return {}
     endif
 
+    let l:initialization_options = {}
+    if has_key(a:linter, 'initialization_options_callback')
+        let l:initialization_options = ale#util#GetFunction(a:linter.initialization_options_callback)(a:buffer)
+    elseif has_key(a:linter, 'initialization_options')
+        let l:initialization_options = a:linter.initialization_options
+    endif
+
     if a:linter.lsp is# 'socket'
         let l:address = ale#linter#GetAddress(a:buffer, a:linter)
         let l:conn_id = ale#lsp#ConnectToAddress(
         \   l:address,
         \   l:root,
         \   a:callback,
+        \   l:initialization_options,
         \)
     else
         let l:executable = ale#linter#GetExecutable(a:buffer, a:linter)
@@ -474,6 +497,7 @@ function! ale#linter#StartLSP(buffer, linter, callback) abort
         \   l:command,
         \   l:root,
         \   a:callback,
+        \   l:initialization_options,
         \)
     endif
 
diff --git a/autoload/ale/lsp.vim b/autoload/ale/lsp.vim
index c1d04db..df4f16d 100644
--- a/autoload/ale/lsp.vim
+++ b/autoload/ale/lsp.vim
@@ -6,7 +6,7 @@
 let s:connections = []
 let g:ale_lsp_next_message_id = 1
 
-function! s:NewConnection() abort
+function! s:NewConnection(initialization_options) abort
     " id: The job ID as a Number, or the server address as a string.
     " data: The message data received so far.
     " executable: An executable only set for program connections.
@@ -18,6 +18,7 @@ function! s:NewConnection() abort
     \   'projects': {},
     \   'open_documents': [],
     \   'callback_list': [],
+    \   'initialization_options': a:initialization_options,
     \}
 
     call add(s:connections, l:conn)
@@ -271,7 +272,7 @@ endfunction
 "
 " The job ID will be returned for for the program if it ran, otherwise
 " 0 will be returned.
-function! ale#lsp#StartProgram(executable, command, project_root, callback) abort
+function! ale#lsp#StartProgram(executable, command, project_root, callback, initialization_options) abort
     if !executable(a:executable)
         return 0
     endif
@@ -279,7 +280,7 @@ function! ale#lsp#StartProgram(executable, command, project_root, callback) abor
     let l:conn = s:FindConnection('executable', a:executable)
 
     " Get the current connection or a new one.
-    let l:conn = !empty(l:conn) ? l:conn : s:NewConnection()
+    let l:conn = !empty(l:conn) ? l:conn : s:NewConnection(a:initialization_options)
     let l:conn.executable = a:executable
 
     if !has_key(l:conn, 'id') || !ale#job#IsRunning(l:conn.id)
@@ -305,10 +306,10 @@ function! ale#lsp#StartProgram(executable, command, project_root, callback) abor
 endfunction
 
 " Connect to an address and set up a callback for handling responses.
-function! ale#lsp#ConnectToAddress(address, project_root, callback) abort
+function! ale#lsp#ConnectToAddress(address, project_root, callback, initialization_options) abort
     let l:conn = s:FindConnection('id', a:address)
     " Get the current connection or a new one.
-    let l:conn = !empty(l:conn) ? l:conn : s:NewConnection()
+    let l:conn = !empty(l:conn) ? l:conn : s:NewConnection(a:initialization_options)
 
     if !has_key(l:conn, 'channel') || ch_status(l:conn.channel) isnot# 'open'
         let l:conn.channnel = ch_open(a:address, {
@@ -383,7 +384,7 @@ function! ale#lsp#Send(conn_id, message, ...) abort
         " Only send the init message once.
         if !l:project.init_request_id
             let [l:init_id, l:init_data] = ale#lsp#CreateMessageData(
-            \   ale#lsp#message#Initialize(l:project_root),
+            \   ale#lsp#message#Initialize(l:project_root, l:conn.initialization_options),
             \)
 
             let l:project.init_request_id = l:init_id
diff --git a/autoload/ale/lsp/message.vim b/autoload/ale/lsp/message.vim
index 5637fa2..1c0499d 100644
--- a/autoload/ale/lsp/message.vim
+++ b/autoload/ale/lsp/message.vim
@@ -24,12 +24,13 @@ function! ale#lsp#message#GetNextVersionID() abort
     return l:id
 endfunction
 
-function! ale#lsp#message#Initialize(root_path) abort
+function! ale#lsp#message#Initialize(root_path, initialization_options) abort
     " TODO: Define needed capabilities.
     return [0, 'initialize', {
     \   'processId': getpid(),
     \   'rootPath': a:root_path,
     \   'capabilities': {},
+    \   'initializationOptions': a:initialization_options,
     \}]
 endfunction
 
diff --git a/doc/ale.txt b/doc/ale.txt
index 66a81f3..0808e2a 100644
--- a/doc/ale.txt
+++ b/doc/ale.txt
@@ -2331,6 +2331,10 @@ ale#linter#Define(filetype, linter)                       *ale#linter#Define()*
                          An optional `completion_filter` callback may be
                          defined for filtering completion results.
 
+                         An optional `initialization_options` or
+                         `initialization_options_callback` may be defined to
+                         pass initialization options to the LSP.
+
   `project_root_callback`  A |String| or |Funcref| for a callback function
                          accepting a buffer number. A |String| should be
                          returned representing the path to the project for the
@@ -2372,6 +2376,17 @@ ale#linter#Define(filetype, linter)                       *ale#linter#Define()*
                          setting can make it easier to guess the linter name
                          by offering a few alternatives.
 
+  `initialization_options` A |Dictionary| of initialization options for LSPs.
+                         This will be fed (as JSON) to the LSP in the
+                         initialize command.
+
+  `initialization_options_callback`
+                         A |String| or |Funcref| for a callback function
+                         accepting a buffer number. A |Dictionary| should be
+                         returned for initialization options to pass the LSP.
+                         This can be used in place of `initialization_options`
+                         when more complicated processing is needed.
+
   Only one of `command`, `command_callback`, or `command_chain` should be
   specified. `command_callback` is generally recommended when a command string
   needs to be generated dynamically, or any global options are used.
diff --git a/test/lsp/test_lsp_client_messages.vader b/test/lsp/test_lsp_client_messages.vader
index 89a29c8..e7eda33 100644
--- a/test/lsp/test_lsp_client_messages.vader
+++ b/test/lsp/test_lsp_client_messages.vader
@@ -16,9 +16,10 @@ Execute(ale#lsp#message#Initialize() should return correct messages):
   \    'processId': getpid(),
   \    'rootPath': '/foo/bar',
   \    'capabilities': {},
+  \    'initializationOptions': {'foo': 'bar'},
   \   }
   \ ],
-  \ ale#lsp#message#Initialize('/foo/bar')
+  \ ale#lsp#message#Initialize('/foo/bar', {'foo': 'bar'})
 
 Execute(ale#lsp#message#Initialized() should return correct messages):
   AssertEqual [1, 'initialized'], ale#lsp#message#Initialized()
diff --git a/test/test_linter_defintion_processing.vader b/test/test_linter_defintion_processing.vader
index 653587b..48a4a39 100644
--- a/test/test_linter_defintion_processing.vader
+++ b/test/test_linter_defintion_processing.vader
@@ -465,3 +465,28 @@ Execute(PreProcess should complain about address_callback for non-LSP linters):
 
   AssertThrows call ale#linter#PreProcess(g:linter)
   AssertEqual '`address_callback` cannot be used when lsp != ''socket''', g:vader_exception
+
+Execute(PreProcess should complain about using initialization_options and initialization_options_callback together):
+  let g:linter = {
+  \ 'name': 'x',
+  \ 'lsp': 'socket',
+  \ 'address_callback': 'X',
+  \ 'language': 'x',
+  \ 'project_root_callback': 'x',
+  \ 'initialization_options': 'x',
+  \ 'initialization_options_callback': 'x',
+  \}
+
+  AssertThrows call ale#linter#PreProcess(g:linter)
+  AssertEqual 'Only one of `initialization_options` or `initialization_options_callback` should be set', g:vader_exception
+
+Execute (PreProcess should throw when initialization_options_callback is not a callback):
+  AssertThrows call ale#linter#PreProcess({
+  \ 'name': 'foo',
+  \ 'lsp': 'socket',
+  \ 'address_callback': 'X',
+  \ 'language': 'x',
+  \ 'project_root_callback': 'x',
+  \ 'initialization_options_callback': {},
+  \})
+  AssertEqual '`initialization_options_callback` must be a callback if defined', g:vader_exception