diff --git a/src/Evaluator/Evaluator.cpp b/src/Evaluator/Evaluator.cpp
index 5525382..94637a7 100644
--- a/src/Evaluator/Evaluator.cpp
+++ b/src/Evaluator/Evaluator.cpp
@@ -175,3 +175,19 @@ shared_ptr<EvalValue> Evaluator::EvaluateFunctionCallExpression(BoundExpression*
 
 }
 
+EvalValue* Evaluator::EvaluateFunction(ScriptFunctionEvalValue *function, vector<EvalValue *> parameters) {
+    auto type = std::dynamic_pointer_cast<FunctionScriptType>(function->GetType());
+    auto parameterTypes = type->GetParameterTypes();
+    auto parameterKeys = type->GetParameterKeys();
+    for (int i = 0; i < parameterTypes->size() && i < parameterKeys->size() && i < parameters.size(); i++){
+        auto parameter = parameters[i];
+        auto requiredType = parameterTypes->at(i);
+        if (*parameter->GetType() != requiredType.get()){
+            throw EvaluationException("Passed wrong type to function.");
+        }
+        auto key = parameterKeys->at(i);
+        this->_evaluationScope->CreateVariable(key->GetScopeId(), key->GetIdentifier(), parameter->Clone());
+    }
+    this->EvaluateBlockStatement(function->GetInnerBlock().get());
+    return nullptr;
+}
\ No newline at end of file
diff --git a/src/Evaluator/Evaluator.hpp b/src/Evaluator/Evaluator.hpp
index e23b06f..3b63ff7 100644
--- a/src/Evaluator/Evaluator.hpp
+++ b/src/Evaluator/Evaluator.hpp
@@ -9,6 +9,7 @@
 #include "EvalValues/NumericEvalValue.hpp"
 #include "EvalValues/StringEvalValue.hpp"
 #include "EvalValues/StringEvalValue.hpp"
+#include "EvalValues/ScriptFunctionEvalValue.hpp"
 #include "EvaluationScope/EvaluationScope.hpp"
 
 using namespace std;
@@ -21,6 +22,7 @@ class Evaluator {
     EvaluationScope* _evaluationScope;
 
     void EvaluateStatement(BoundStatement* statement);
+    void EvaluateBlockStatement(BoundBlockStatement* statement);
     void EvaluateExpressionStatement(BoundExpressionStatement* statement);
     void EvaluateAssignmentStatement(BoundAssignmentStatement* statement);
     void EvaluateFunctionDeclarationStatement(BoundFunctionDeclarationStatement *statement);
@@ -52,7 +54,7 @@ public:
     }
 
     void Evaluate(BoundScriptStatement* statement);
-    void EvaluateBlockStatement(BoundBlockStatement* statement);
+    EvalValue* EvaluateFunction(ScriptFunctionEvalValue* func, vector<EvalValue*> parameters);
 
     EvaluationScope* GetScope(){
         return _evaluationScope;
diff --git a/src/Script.cpp b/src/Script.cpp
index 979fc38..7d3fdcc 100644
--- a/src/Script.cpp
+++ b/src/Script.cpp
@@ -1,3 +1,5 @@
+#include <utility>
+
 #include <utility>
 #include <unordered_map>
 #include "Script.hpp"
@@ -65,6 +67,16 @@ EvalValue *Script::GetLastValue() {
     return _evaluator->GetLastValue();
 }
 
+bool Script::HasFunction(const string &key) {
+    auto f = _scriptVariables->find(HashedString(key).GetHash());
+    return f != _scriptVariables->end() && f.operator->()->second->GetType()->GetClass() == TypeClass ::Function;
+}
+
+EvalValue *Script::CallFunction(const string &key, vector<EvalValue *> variables) {
+    auto var = (ScriptFunctionEvalValue*)GetVariable(key);
+    return this->_evaluator->EvaluateFunction(var, std::move(variables));
+}
+
 extern "C" {
     Script* CreateScript(char * s){
         return Script::Create(s);
diff --git a/src/Script.hpp b/src/Script.hpp
index 5179ff3..589dc37 100644
--- a/src/Script.hpp
+++ b/src/Script.hpp
@@ -36,6 +36,9 @@ public:
     EvalValue* GetVariable(const string& key);
     bool HasVariable(const string& key);
 
+    EvalValue* CallFunction(const string& key, vector<EvalValue*> variables);
+    bool HasFunction(const string& key);
+
 
 };
 
diff --git a/tests/integration/ExternFunctionsTests.cpp b/tests/integration/ExternFunctionsTests.cpp
deleted file mode 100644
index b28b04f..0000000
--- a/tests/integration/ExternFunctionsTests.cpp
+++ /dev/null
@@ -1,3 +0,0 @@
-
-
-
diff --git a/tests/integration/Functions.cpp b/tests/integration/Functions.cpp
index 1939308..98a44d5 100644
--- a/tests/integration/Functions.cpp
+++ b/tests/integration/Functions.cpp
@@ -38,4 +38,20 @@ TEST_CASE( "Define script function and call multiple times", "[integration]" ) {
     delete script;
 }
 
+TEST_CASE( "Define script function and call from extern", "[integration]" ) {
+    Script* script = Script::Create("result = 0 function add(number a) result = result + a end");
+    REQUIRE(!script->Diagnostics -> HasErrors());
+    script->Evaluate();
+
+    REQUIRE(script->HasFunction("add"));
+    script->CallFunction("add", {new IntegerEvalValue(5)});
+    script->CallFunction("add", {new IntegerEvalValue(6)});
+
+    auto result = script->GetVariable("result");
+    REQUIRE(result->GetType()->GetClass() == TypeClass::Number);
+    REQUIRE(result->EvaluateInteger() == 11);
+    delete script;
+}
+
+
 #endif