diff --git a/cli/command/completion/functions.go b/cli/command/completion/functions.go
index 7777cb8427..b395850b45 100644
--- a/cli/command/completion/functions.go
+++ b/cli/command/completion/functions.go
@@ -2,6 +2,7 @@ package completion
 
 import (
 	"os"
+	"strings"
 
 	"github.com/docker/cli/cli/command/formatter"
 	"github.com/docker/docker/api/types/container"
@@ -105,6 +106,29 @@ func NetworkNames(dockerCLI APIClientProvider) ValidArgsFn {
 	}
 }
 
+// EnvVarNames offers completion for environment-variable names. This
+// completion can be used for "--env" and "--build-arg" flags, which
+// allow obtaining the value of the given environment-variable if present
+// in the local environment, so we only should complete the names of the
+// environment variables, and not their value. This also prevents the
+// completion script from printing values of environment variables
+// containing sensitive values.
+//
+// For example;
+//
+//	export MY_VAR=hello
+//	docker run --rm --env MY_VAR alpine printenv MY_VAR
+//	hello
+func EnvVarNames(_ *cobra.Command, _ []string, _ string) (names []string, _ cobra.ShellCompDirective) {
+	envs := os.Environ()
+	names = make([]string, 0, len(envs))
+	for _, env := range envs {
+		name, _, _ := strings.Cut(env, "=")
+		names = append(names, name)
+	}
+	return names, cobra.ShellCompDirectiveNoFileComp
+}
+
 // FileNames is a convenience function to use [cobra.ShellCompDirectiveDefault],
 // which indicates to let the shell perform its default behavior after
 // completions have been provided.
diff --git a/cli/command/container/exec.go b/cli/command/container/exec.go
index 1f5506ae2a..c2a1d44799 100644
--- a/cli/command/container/exec.go
+++ b/cli/command/container/exec.go
@@ -4,7 +4,6 @@ import (
 	"context"
 	"fmt"
 	"io"
-	"os"
 
 	"github.com/docker/cli/cli"
 	"github.com/docker/cli/cli/command"
@@ -78,9 +77,7 @@ func NewExecCommand(dockerCli command.Cli) *cobra.Command {
 	flags.StringVarP(&options.Workdir, "workdir", "w", "", "Working directory inside the container")
 	flags.SetAnnotation("workdir", "version", []string{"1.35"})
 
-	_ = cmd.RegisterFlagCompletionFunc("env", func(*cobra.Command, []string, string) ([]string, cobra.ShellCompDirective) {
-		return os.Environ(), cobra.ShellCompDirectiveNoFileComp
-	})
+	_ = cmd.RegisterFlagCompletionFunc("env", completion.EnvVarNames)
 	_ = cmd.RegisterFlagCompletionFunc("env-file", completion.FileNames)
 
 	return cmd
diff --git a/cli/command/container/run.go b/cli/command/container/run.go
index bdf8eff5be..5fb44baef3 100644
--- a/cli/command/container/run.go
+++ b/cli/command/container/run.go
@@ -4,7 +4,6 @@ import (
 	"context"
 	"fmt"
 	"io"
-	"os"
 	"strings"
 	"syscall"
 
@@ -70,9 +69,7 @@ func NewRunCommand(dockerCli command.Cli) *cobra.Command {
 	command.AddTrustVerificationFlags(flags, &options.untrusted, dockerCli.ContentTrustEnabled())
 	copts = addFlags(flags)
 
-	_ = cmd.RegisterFlagCompletionFunc("env", func(*cobra.Command, []string, string) ([]string, cobra.ShellCompDirective) {
-		return os.Environ(), cobra.ShellCompDirectiveNoFileComp
-	})
+	_ = cmd.RegisterFlagCompletionFunc("env", completion.EnvVarNames)
 	_ = cmd.RegisterFlagCompletionFunc("env-file", completion.FileNames)
 	_ = cmd.RegisterFlagCompletionFunc("network", completion.NetworkNames(dockerCli))
 	return cmd