diff --git a/src/qt/bitcoin.h b/src/qt/bitcoin.h
--- a/src/qt/bitcoin.h
+++ b/src/qt/bitcoin.h
@@ -73,8 +73,8 @@
     void parameterSetup();
     /// Create options model
     void createOptionsModel(bool resetSettings);
-    /// Update prune value
-    void SetPrune(bool prune, bool force = false);
+    /// Initialize prune setting
+    void InitializePruneSetting(bool prune);
     /// Create main window
     void createWindow(const Config *, const NetworkStyle *networkStyle);
     /// Create splash screen
diff --git a/src/qt/bitcoin.cpp b/src/qt/bitcoin.cpp
--- a/src/qt/bitcoin.cpp
+++ b/src/qt/bitcoin.cpp
@@ -320,8 +320,10 @@
     InitParameterInteraction(gArgs);
 }
 
-void BitcoinApplication::SetPrune(bool prune, bool force) {
-    optionsModel->SetPrune(prune, force);
+void BitcoinApplication::InitializePruneSetting(bool prune) {
+    // If prune is set, intentionally override existing prune size with
+    // the default size since this is called when choosing a new datadir.
+    optionsModel->SetPruneTargetGB(prune ? DEFAULT_PRUNE_TARGET_GB : 0, true);
 }
 
 void BitcoinApplication::requestInitialize(
@@ -748,7 +750,7 @@
 
     if (did_show_intro) {
         // Store intro dialog settings other than datadir (network specific)
-        app.SetPrune(prune, true);
+        app.InitializePruneSetting(prune);
     }
 
     // Get global config
diff --git a/src/qt/guiconstants.h b/src/qt/guiconstants.h
--- a/src/qt/guiconstants.h
+++ b/src/qt/guiconstants.h
@@ -51,4 +51,7 @@
 /* One gigabyte (GB) in bytes */
 static constexpr uint64_t GB_BYTES{1'000'000'000};
 
+// Default prune target displayed in GUI.
+static constexpr int DEFAULT_PRUNE_TARGET_GB{2};
+
 #endif // BITCOIN_QT_GUICONSTANTS_H
diff --git a/src/qt/intro.cpp b/src/qt/intro.cpp
--- a/src/qt/intro.cpp
+++ b/src/qt/intro.cpp
@@ -130,9 +130,10 @@
         ui->prune->setChecked(true);
         ui->prune->setEnabled(false);
     }
-    ui->prune->setText(tr("Discard blocks after verification, except most "
-                          "recent %1 GB (prune)")
-                           .arg(pruneTarget ? pruneTarget / 1000 : 2));
+    ui->prune->setText(
+        tr("Discard blocks after verification, except most "
+           "recent %1 GB (prune)")
+            .arg(pruneTarget ? pruneTarget / 1000 : DEFAULT_PRUNE_TARGET_GB));
     requiredSpace = m_blockchain_size;
     QString storageRequiresMsg =
         tr("At least %1 GB of data will be stored in this directory, and it "
diff --git a/src/qt/optionsmodel.h b/src/qt/optionsmodel.h
--- a/src/qt/optionsmodel.h
+++ b/src/qt/optionsmodel.h
@@ -85,7 +85,8 @@
     }
 
     /* Explicit setters */
-    void SetPrune(bool prune, bool force = false);
+    void SetPruneEnabled(bool prune, bool force = false);
+    void SetPruneTargetGB(int prune_target_gb, bool force = false);
 
     /* Restart flag helper */
     void setRestartRequired(bool fRequired);
diff --git a/src/qt/optionsmodel.cpp b/src/qt/optionsmodel.cpp
--- a/src/qt/optionsmodel.cpp
+++ b/src/qt/optionsmodel.cpp
@@ -102,9 +102,9 @@
         settings.setValue("bPrune", false);
     }
     if (!settings.contains("nPruneSize")) {
-        settings.setValue("nPruneSize", 2);
+        settings.setValue("nPruneSize", DEFAULT_PRUNE_TARGET_GB);
     }
-    SetPrune(settings.value("bPrune").toBool());
+    SetPruneEnabled(settings.value("bPrune").toBool());
 
     if (!settings.contains("nDatabaseCache")) {
         settings.setValue("nDatabaseCache", (qint64)DEFAULT_DB_CACHE_MB);
@@ -283,7 +283,7 @@
         .arg(DEFAULT_GUI_PROXY_PORT);
 }
 
-void OptionsModel::SetPrune(bool prune, bool force) {
+void OptionsModel::SetPruneEnabled(bool prune, bool force) {
     QSettings settings;
     settings.setValue("bPrune", prune);
     // Convert prune size from GB to MiB:
@@ -299,6 +299,15 @@
     }
 }
 
+void OptionsModel::SetPruneTargetGB(int prune_target_gb, bool force) {
+    const bool prune = prune_target_gb > 0;
+    if (prune) {
+        QSettings settings;
+        settings.setValue("nPruneSize", prune_target_gb);
+    }
+    SetPruneEnabled(prune, force);
+}
+
 // read QSettings values and return them
 QVariant OptionsModel::data(const QModelIndex &index, int role) const {
     if (role == Qt::EditRole) {