diff --git a/src/java/org/apache/poi/ss/formula/atp/AnalysisToolPak.java b/src/java/org/apache/poi/ss/formula/atp/AnalysisToolPak.java
index 373b653827..f91cbfc798 100644
--- a/src/java/org/apache/poi/ss/formula/atp/AnalysisToolPak.java
+++ b/src/java/org/apache/poi/ss/formula/atp/AnalysisToolPak.java
@@ -112,7 +112,7 @@ public final class AnalysisToolPak implements UDFFinder {
         r(m, "HEX2OCT", null);
         r(m, "IFERROR", IfError.instance);
         r(m, "IMABS", null);
-        r(m, "IMAGINARY", null);
+        r(m, "IMAGINARY", Imaginary.instance);
         r(m, "IMARGUMENT", null);
         r(m, "IMCONJUGATE", null);
         r(m, "IMCOS", null);
diff --git a/src/java/org/apache/poi/ss/formula/functions/Imaginary.java b/src/java/org/apache/poi/ss/formula/functions/Imaginary.java
new file mode 100644
index 0000000000..2b1309310d
--- /dev/null
+++ b/src/java/org/apache/poi/ss/formula/functions/Imaginary.java
@@ -0,0 +1,109 @@
+/* ====================================================================
+   Licensed to the Apache Software Foundation (ASF) under one or more
+   contributor license agreements.  See the NOTICE file distributed with
+   this work for additional information regarding copyright ownership.
+   The ASF licenses this file to You under the Apache License, Version 2.0
+   (the "License"); you may not use this file except in compliance with
+   the License.  You may obtain a copy of the License at
+
+       http://www.apache.org/licenses/LICENSE-2.0
+
+   Unless required by applicable law or agreed to in writing, software
+   distributed under the License is distributed on an "AS IS" BASIS,
+   WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+   See the License for the specific language governing permissions and
+   limitations under the License.
+==================================================================== */
+
+package org.apache.poi.ss.formula.functions;
+
+import org.apache.poi.ss.formula.OperationEvaluationContext;
+import org.apache.poi.ss.formula.eval.*;
+
+import java.util.regex.Matcher;
+import java.util.regex.Pattern;
+
+/**
+ * Implementation for Excel IMAGINARY() function.<p/>
+ * <p/>
+ * <b>Syntax</b>:<br/> <b>IMAGINARY  </b>(<b>Inumber</b>)<br/>
+ * <p/>
+ * Returns the imaginary coefficient of a complex number in x + yi or x + yj text format.
+ * <p/>
+ * Inumber     is a complex number for which you want the imaginary coefficient.
+ * <p/>
+ * Remarks
+ * <ul>
+ * <li>Use COMPLEX to convert real and imaginary coefficients into a complex number.</li>
+ * </ul>
+ *
+ * @author cedric dot walter @ gmail dot com
+ */
+public class Imaginary extends Fixed1ArgFunction implements FreeRefFunction {
+
+    public static final FreeRefFunction instance = new Imaginary();
+
+    public static final String GROUP1_REAL_SIGN_REGEX = "([+-]?)";
+    public static final String GROUP2_REAL_INTEGER_OR_DOUBLE_REGEX = "([0-9]+\\.[0-9]+|[0-9]*)";
+    public static final String GROUP3_IMAGINARY_SIGN_REGEX = "([+-]?)";
+    public static final String GROUP4_IMAGINARY_INTEGER_OR_DOUBLE_REGEX = "([0-9]+\\.[0-9]+|[0-9]*)";
+    public static final String GROUP5_IMAGINARY_GROUP_REGEX = "([ij]?)";
+
+    public static final Pattern COMPLEX_NUMBER_PATTERN
+            = Pattern.compile(GROUP1_REAL_SIGN_REGEX + GROUP2_REAL_INTEGER_OR_DOUBLE_REGEX +
+            GROUP3_IMAGINARY_SIGN_REGEX + GROUP4_IMAGINARY_INTEGER_OR_DOUBLE_REGEX + GROUP5_IMAGINARY_GROUP_REGEX);
+
+    public static final int GROUP1_REAL_SIGN = 1;
+    public static final int GROUP2_IMAGINARY_INTEGER_OR_DOUBLE = 2;
+    public static final int GROUP3_IMAGINARY_SIGN = 3;
+    public static final int GROUP4_IMAGINARY_INTEGER_OR_DOUBLE = 4;
+
+    public ValueEval evaluate(int srcRowIndex, int srcColumnIndex, ValueEval inumberVE) {
+        ValueEval veText1;
+        try {
+            veText1 = OperandResolver.getSingleValue(inumberVE, srcRowIndex, srcColumnIndex);
+        } catch (EvaluationException e) {
+            return e.getErrorEval();
+        }
+        String iNumber = OperandResolver.coerceValueToString(veText1);
+
+        Matcher m = COMPLEX_NUMBER_PATTERN.matcher(iNumber);
+        boolean result = m.matches();
+
+        String imaginary = "";
+        if (result == true) {
+            String imaginaryGroup = m.group(5);
+            boolean hasImaginaryPart = imaginaryGroup.equals("i") || imaginaryGroup.equals("j");
+
+            if (imaginaryGroup.length() == 0) {
+                return new StringEval(String.valueOf(0));
+            }
+
+            if (hasImaginaryPart) {
+                String sign = "";
+                String imaginarySign = m.group(GROUP3_IMAGINARY_SIGN);
+                if (imaginarySign.length() != 0 && !(imaginarySign.equals("+"))) {
+                    sign = imaginarySign;
+                }
+
+                String groupImaginaryNumber = m.group(GROUP4_IMAGINARY_INTEGER_OR_DOUBLE);
+                if (groupImaginaryNumber.length() != 0) {
+                    imaginary = sign + groupImaginaryNumber;
+                } else {
+                    imaginary = sign + "1";
+                }
+            }
+        } else {
+            return ErrorEval.NUM_ERROR;
+        }
+
+        return new StringEval(imaginary);
+    }
+
+    public ValueEval evaluate(ValueEval[] args, OperationEvaluationContext ec) {
+        if (args.length != 1) {
+            return ErrorEval.VALUE_INVALID;
+        }
+        return evaluate(ec.getRowIndex(), ec.getColumnIndex(), args[0]);
+    }
+}
diff --git a/src/testcases/org/apache/poi/ss/formula/functions/TestImaginaryFunctionsFromSpreadsheet.java b/src/testcases/org/apache/poi/ss/formula/functions/TestImaginaryFunctionsFromSpreadsheet.java
new file mode 100644
index 0000000000..c5b74ac0c7
--- /dev/null
+++ b/src/testcases/org/apache/poi/ss/formula/functions/TestImaginaryFunctionsFromSpreadsheet.java
@@ -0,0 +1,30 @@
+/* ====================================================================
+   Licensed to the Apache Software Foundation (ASF) under one or more
+   contributor license agreements.  See the NOTICE file distributed with
+   this work for additional information regarding copyright ownership.
+   The ASF licenses this file to You under the Apache License, Version 2.0
+   (the "License"); you may not use this file except in compliance with
+   the License.  You may obtain a copy of the License at
+
+       http://www.apache.org/licenses/LICENSE-2.0
+
+   Unless required by applicable law or agreed to in writing, software
+   distributed under the License is distributed on an "AS IS" BASIS,
+   WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+   See the License for the specific language governing permissions and
+   limitations under the License.
+==================================================================== */
+
+package org.apache.poi.ss.formula.functions;
+
+/**
+ * Tests Imaginary() as loaded from a test data spreadsheet.<p/>
+ *
+ * @author cedric dot walter @ gmail dot com
+ */
+public class TestImaginaryFunctionsFromSpreadsheet extends BaseTestFunctionsFromSpreadsheet {
+
+    protected String getFilename() {
+        return "ImaginaryFunctionTestCaseData.xls";
+    }
+}
diff --git a/test-data/spreadsheet/FormulaEvalTestData.xls b/test-data/spreadsheet/FormulaEvalTestData.xls
index c585b823ef..ff8e932ac1 100644
Binary files a/test-data/spreadsheet/FormulaEvalTestData.xls and b/test-data/spreadsheet/FormulaEvalTestData.xls differ
diff --git a/test-data/spreadsheet/ImaginaryFunctionTestCaseData.xls b/test-data/spreadsheet/ImaginaryFunctionTestCaseData.xls
new file mode 100644
index 0000000000..ce079f3200
Binary files /dev/null and b/test-data/spreadsheet/ImaginaryFunctionTestCaseData.xls differ