diff --git a/config-merge.js b/config-merge.js
index 4b468df..24f88e7 100644
--- a/config-merge.js
+++ b/config-merge.js
@@ -1,6 +1,6 @@
 const fs = require('fs')
 const glob = require('glob')
-const merge = require('lodash.merge')
+const mergeWith = require('lodash.mergewith')
 const path = require('path')
 const YAML = require('yaml')
 const toml = require('toml-j0.4')
@@ -20,6 +20,7 @@ const envReserved = new Set(["_", "SHLVL"])
 // prints the help message
 function printHelp() {
     console.error("boxboat/config-merge [flags] file1 [file2] ... [fileN]")
+    console.error("-a, --array    merge|overwrite|concat    whether to merge, overwrite, or concatenate arrays.  defaults to merge")
     console.error("-f, --format   json|toml|yaml    whether to output json, toml, or yaml.  defaults to yaml")
     console.error("-h  --help     print the help message")
     console.error("    files ending in .env and .sh will be sourced and used for environment variable substitution")
@@ -57,6 +58,7 @@ function readFileAndSubEnv(file) {
 let args = process.argv.slice(2)
 let processPositional = true
 let setFlag = null
+let array = 'merge'
 let format = 'yaml'
 let obj = {}
 
@@ -76,7 +78,16 @@ for (let arg of args) {
             printHelp()
             process.exit(0)
         }
-        if (setFlag == "f") {
+        if (setFlag == "a") {
+            if (arg == "merge" || arg == "overwrite" || arg == "concat") {
+                array = arg
+                setFlag = null
+            } else {
+                console.error(`Array should be "merge", "overwrite", or "concat", invalid: ${arg}`)
+                printHelp()
+                process.exit(1)
+            }
+        } else if (setFlag == "f") {
             if (arg == "json" || arg == "toml" || arg == "yaml") {
                 format = arg
                 setFlag = null
@@ -85,10 +96,13 @@ for (let arg of args) {
                 printHelp()
                 process.exit(1)
             }
+        } else if (arg == "-a" || arg == "--array") {
+            setFlag = "a"
         }
         else if (arg == "-f" || arg == "--foramt") {
             setFlag = "f"
-        } else {
+        }
+        else {
             break
         }
         positionalArgCount++
@@ -110,6 +124,18 @@ for (let arg of args) {
     }
 }
 
+// merge customizer
+function customizer(objValue, srcValue) {
+    if (Array.isArray(objValue)) {
+        if (array == "overwrite") {
+            return srcValue
+        } else if (array == "concat") {
+            return objValue.concat(srcValue)
+        }
+    }
+    return undefined
+}
+
 // process files
 for (arg of globArgs) {
     // check that file exists
@@ -152,13 +178,13 @@ for (arg of globArgs) {
             }
         }
         else if (arg.match(mergeJsonRe)) {
-            merge(obj, JSON.parse(readFileAndSubEnv(arg)))
+            mergeWith(obj, JSON.parse(readFileAndSubEnv(arg)), customizer)
         }
         else if (arg.match(mergeTomlRe)) {
-            merge(obj, toml.parse(readFileAndSubEnv(arg)))
+            mergeWith(obj, toml.parse(readFileAndSubEnv(arg)), customizer)
         }
         else if (arg.match(mergeYamlRe)) {
-            merge(obj, YAML.parse(readFileAndSubEnv(arg)))
+            mergeWith(obj, YAML.parse(readFileAndSubEnv(arg)), customizer)
         } else {
             console.error(`Invalid file extension: ${arg}`)
             printHelp()
diff --git a/package.json b/package.json
index 3451d24..e47be38 100644
--- a/package.json
+++ b/package.json
@@ -5,7 +5,7 @@
   "dependencies": {
     "fast-json-patch": "2.0.6",
     "glob": "7.1.2",
-    "lodash.merge": "4.6.2",
+    "lodash.mergewith": "4.6.2",
     "toml-j0.4": "1.1.1",
     "tomlify-j0.4": "3.0.0",
     "yaml": "1.10.0"
diff --git a/test.sh b/test.sh
index 3ab951f..d375f00 100755
--- a/test.sh
+++ b/test.sh
@@ -16,13 +16,27 @@ docker run --rm \
     -f toml "*"
 echo ""
 
-echo "YAML:"
+echo "YAML array merge:"
 docker run --rm \
     -v "$(pwd)/test/mix/:/home/node/" \
     boxboat/config-merge \
     "*"
 echo ""
 
+echo "YAML array overwrite:"
+docker run --rm \
+    -v "$(pwd)/test/mix/:/home/node/" \
+    boxboat/config-merge \
+    -a overwrite "*"
+echo ""
+
+echo "YAML array concat:"
+docker run --rm \
+    -v "$(pwd)/test/mix/:/home/node/" \
+    boxboat/config-merge \
+    -a concat "*"
+echo ""
+
 echo "Docker Compose"
 docker run --rm \
     -v "$(pwd)/test/docker-compose/:/home/node/" \
diff --git a/test/mix/10.yaml b/test/mix/10.yaml
index 6bad445..190015e 100644
--- a/test/mix/10.yaml
+++ b/test/mix/10.yaml
@@ -1 +1,3 @@
-override-yaml: override
\ No newline at end of file
+override-yaml: override
+array-obj:
+  - key3: key3
diff --git a/yarn.lock b/yarn.lock
index 129e863..6411514 100644
--- a/yarn.lock
+++ b/yarn.lock
@@ -53,9 +53,10 @@ inherits@2:
   version "2.0.3"
   resolved "https://registry.yarnpkg.com/inherits/-/inherits-2.0.3.tgz#633c2c83e3da42a502f52466022480f4208261de"
 
-lodash.merge@4.6.2:
+lodash.mergewith@4.6.2:
   version "4.6.2"
-  resolved "https://registry.yarnpkg.com/lodash.merge/-/lodash.merge-4.6.2.tgz#558aa53b43b661e1925a0afdfa36a9a1085fe57a"
+  resolved "https://registry.yarnpkg.com/lodash.mergewith/-/lodash.mergewith-4.6.2.tgz#617121f89ac55f59047c7aec1ccd6654c6590f55"
+  integrity sha512-GK3g5RPZWTRSeLSpgP8Xhra+pnjBC56q9FZYe1d5RN3TJ35dbkGy3YqBSMbyCrlbi+CM9Z3Jk5yTL7RCsqboyQ==
 
 minimatch@^3.0.4:
   version "3.0.4"
@@ -85,7 +86,7 @@ wrappy@1:
   version "1.0.2"
   resolved "https://registry.yarnpkg.com/wrappy/-/wrappy-1.0.2.tgz#b5243d8f3ec1aa35f1364605bc0d1036e30ab69f"
 
-yaml@^1.10.0:
+yaml@1.10.0:
   version "1.10.0"
   resolved "https://registry.yarnpkg.com/yaml/-/yaml-1.10.0.tgz#3b593add944876077d4d683fee01081bd9fff31e"
   integrity sha512-yr2icI4glYaNG+KWONODapy2/jDdMSDnrONSjblABjD9B4Z5LgiircSt8m8sRZFNi08kG9Sm0uSHtEmP3zaEGg==