diff --git a/tools/lammps-gui/CMakeLists.txt b/tools/lammps-gui/CMakeLists.txt
index 5ac23daac7..057d686b12 100644
--- a/tools/lammps-gui/CMakeLists.txt
+++ b/tools/lammps-gui/CMakeLists.txt
@@ -130,6 +130,8 @@ set(PROJECT_SOURCES
   codeeditor.h
   findandreplace.cpp
   findandreplace.h
+  flagwarnings.cpp
+  flagwarnings.h
   helpers.cpp
   highlighter.cpp
   highlighter.h
diff --git a/tools/lammps-gui/TODO.md b/tools/lammps-gui/TODO.md
index 3bb8c8d3dd..c9c8d26568 100644
--- a/tools/lammps-gui/TODO.md
+++ b/tools/lammps-gui/TODO.md
@@ -3,7 +3,6 @@ LAMMPS-GUI TODO list:
 # Short term goals (v1.x)
 
 - add wizards for all tutorials. try to reduce redundant code in wizards.
-- add a highlighting to the log window that highlights warnings
 - add a preferences option to override light/dark theme setting and add choice for theme
 - implement a timed "Auto-Save" feature that saves after some idle time.  set timeout in Editor preferences.
 - add a "Filter data" checkbox to the "Charts" window to select whether data should be dropped.
diff --git a/tools/lammps-gui/flagwarnings.cpp b/tools/lammps-gui/flagwarnings.cpp
new file mode 100644
index 0000000000..8c0a4c4cde
--- /dev/null
+++ b/tools/lammps-gui/flagwarnings.cpp
@@ -0,0 +1,44 @@
+/* ----------------------------------------------------------------------
+   LAMMPS - Large-scale Atomic/Molecular Massively Parallel Simulator
+   https://www.lammps.org/, Sandia National Laboratories
+   LAMMPS development team: developers@lammps.org
+
+   Copyright (2003) Sandia Corporation.  Under the terms of Contract
+   DE-AC04-94AL85000 with Sandia Corporation, the U.S. Government retains
+   certain rights in this software.  This software is distributed under
+   the GNU General Public License.
+
+   See the README file in the top-level LAMMPS directory.
+------------------------------------------------------------------------- */
+
+#include "flagwarnings.h"
+
+#include "helpers.h"
+
+#include <QColor>
+#include <QFont>
+
+// workaround for Qt-5.12
+#if QT_VERSION < QT_VERSION_CHECK(5, 14, 0)
+namespace QColorConstants {
+const QColor Red     = QColor::fromRgb(0xff, 0x00, 0x00);
+} // namespace QColorConstants
+#endif
+
+FlagWarnings::FlagWarnings(QTextDocument *parent) :
+    QSyntaxHighlighter(parent), isWarning(QStringLiteral("^(ERROR|WARNING).*$"))
+{
+    formatWarning.setForeground(QColorConstants::Red);
+    formatWarning.setFontWeight(QFont::Bold);
+}
+
+void FlagWarnings::highlightBlock(const QString &text)
+{
+    // nothing to do for empty lines
+    if (text.isEmpty()) return;
+
+    auto match = isWarning.match(text);
+    if (match.hasMatch()) {
+        setFormat(match.capturedStart(0), match.capturedLength(0), formatWarning);
+    }
+}
diff --git a/tools/lammps-gui/flagwarnings.h b/tools/lammps-gui/flagwarnings.h
new file mode 100644
index 0000000000..b34f1eba6a
--- /dev/null
+++ b/tools/lammps-gui/flagwarnings.h
@@ -0,0 +1,37 @@
+/* -*- c++ -*- ----------------------------------------------------------
+   LAMMPS - Large-scale Atomic/Molecular Massively Parallel Simulator
+   https://www.lammps.org/, Sandia National Laboratories
+   LAMMPS development team: developers@lammps.org
+
+   Copyright (2003) Sandia Corporation.  Under the terms of Contract
+   DE-AC04-94AL85000 with Sandia Corporation, the U.S. Government retains
+   certain rights in this software.  This software is distributed under
+   the GNU General Public License.
+
+   See the README file in the top-level LAMMPS directory.
+------------------------------------------------------------------------- */
+
+#ifndef FLAGWARNINGS_H
+#define FLAGWARNINGS_H
+
+#include <QRegularExpression>
+#include <QSyntaxHighlighter>
+#include <QTextCharFormat>
+
+class FlagWarnings : public QSyntaxHighlighter {
+    Q_OBJECT
+
+public:
+    FlagWarnings(QTextDocument *parent = 0);
+
+protected:
+    void highlightBlock(const QString &text) override;
+
+private:
+    QRegularExpression isWarning;
+    QTextCharFormat formatWarning;
+};
+#endif
+// Local Variables:
+// c-basic-offset: 4
+// End:
diff --git a/tools/lammps-gui/logwindow.cpp b/tools/lammps-gui/logwindow.cpp
index 4527bcb0dd..85ed1d8744 100644
--- a/tools/lammps-gui/logwindow.cpp
+++ b/tools/lammps-gui/logwindow.cpp
@@ -13,6 +13,7 @@
 
 #include "logwindow.h"
 
+#include "flagwarnings.h"
 #include "lammpsgui.h"
 
 #include <QAction>
@@ -33,11 +34,13 @@ const QString LogWindow::yaml_regex =
     QStringLiteral("^(keywords:.*$|data:$|---$|\\.\\.\\.$|  - \\[.*\\]$)");
 
 LogWindow::LogWindow(const QString &_filename, QWidget *parent) :
-    QPlainTextEdit(parent), filename(_filename)
+    QPlainTextEdit(parent), filename(_filename), warnings(nullptr)
 {
     QSettings settings;
     resize(settings.value("logx", 500).toInt(), settings.value("logy", 320).toInt());
 
+    warnings = new FlagWarnings(document());
+
     auto *action = new QShortcut(QKeySequence(Qt::CTRL | Qt::Key_S), this);
     connect(action, &QShortcut::activated, this, &LogWindow::save_as);
     action = new QShortcut(QKeySequence(Qt::CTRL | Qt::Key_Y), this);
@@ -50,6 +53,11 @@ LogWindow::LogWindow(const QString &_filename, QWidget *parent) :
     installEventFilter(this);
 }
 
+LogWindow::~LogWindow()
+{
+    delete warnings;
+}
+
 void LogWindow::closeEvent(QCloseEvent *event)
 {
     QSettings settings;
diff --git a/tools/lammps-gui/logwindow.h b/tools/lammps-gui/logwindow.h
index b6cf78c48f..84240b6e70 100644
--- a/tools/lammps-gui/logwindow.h
+++ b/tools/lammps-gui/logwindow.h
@@ -16,11 +16,14 @@
 
 #include <QPlainTextEdit>
 
+class FlagWarnings;
+
 class LogWindow : public QPlainTextEdit {
     Q_OBJECT
 
 public:
     LogWindow(const QString &filename, QWidget *parent = nullptr);
+    ~LogWindow() override;
 
 private slots:
     void extract_yaml();
@@ -37,6 +40,7 @@ protected:
 private:
     QString filename;
     static const QString yaml_regex;
+    FlagWarnings *warnings;
 };
 
 #endif