diff --git a/completions/bash/brew b/completions/bash/brew
index b85bd4746c..9b11a30207 100644
--- a/completions/bash/brew
+++ b/completions/bash/brew
@@ -2588,6 +2588,7 @@ _brew_tests() {
       --fail-fast
       --generic
       --help
+      --no-parallel
       --online
       --only
       --profile
diff --git a/completions/fish/brew.fish b/completions/fish/brew.fish
index d6a8a66be7..04701edb8d 100644
--- a/completions/fish/brew.fish
+++ b/completions/fish/brew.fish
@@ -1693,6 +1693,7 @@ __fish_brew_complete_arg 'tests' -l debug -d 'Enable debugging using `ruby/debug
 __fish_brew_complete_arg 'tests' -l fail-fast -d 'Exit early on the first failing test'
 __fish_brew_complete_arg 'tests' -l generic -d 'Run only OS-agnostic tests'
 __fish_brew_complete_arg 'tests' -l help -d 'Show this message'
+__fish_brew_complete_arg 'tests' -l no-parallel -d 'Run tests serially'
 __fish_brew_complete_arg 'tests' -l online -d 'Include tests that use the GitHub API and tests that use any of the taps for official external commands'
 __fish_brew_complete_arg 'tests' -l only -d 'Run only `test_script_spec.rb`. Appending `:line_number` will start at a specific line'
 __fish_brew_complete_arg 'tests' -l profile -d 'Run the test suite serially to find the n slowest tests'
diff --git a/completions/zsh/_brew b/completions/zsh/_brew
index 4b9ccf6820..fe82678362 100644
--- a/completions/zsh/_brew
+++ b/completions/zsh/_brew
@@ -2081,6 +2081,7 @@ _brew_tests() {
     '--fail-fast[Exit early on the first failing test]' \
     '--generic[Run only OS-agnostic tests]' \
     '--help[Show this message]' \
+    '--no-parallel[Run tests serially]' \
     '--online[Include tests that use the GitHub API and tests that use any of the taps for official external commands]' \
     '(--changed)--only[Run only `test_script_spec.rb`. Appending `:line_number` will start at a specific line]' \
     '--profile[Run the test suite serially to find the n slowest tests]' \
diff --git a/docs/Manpage.md b/docs/Manpage.md
index f77caf47a4..ade5e545ce 100644
--- a/docs/Manpage.md
+++ b/docs/Manpage.md
@@ -3211,6 +3211,10 @@ Run Homebrew's unit and integration tests.
 
 : Exit early on the first failing test.
 
+`--no-parallel`
+
+: Run tests serially.
+
 `--only`
 
 : Run only `<test_script>_spec.rb`. Appending `:<line_number>` will start at a
diff --git a/manpages/brew.1 b/manpages/brew.1
index d542a44ac4..3108a75159 100644
--- a/manpages/brew.1
+++ b/manpages/brew.1
@@ -2039,6 +2039,9 @@ Only runs tests on files that were changed from the master branch\.
 \fB\-\-fail\-fast\fP
 Exit early on the first failing test\.
 .TP
+\fB\-\-no\-parallel\fP
+Run tests serially\.
+.TP
 \fB\-\-only\fP
 Run only \fB<test_script>_spec\.rb\fP\&\. Appending \fB:<line_number>\fP will start at a specific line\.
 .TP