diff --git a/lib/pdk/cli.rb b/lib/pdk/cli.rb
index 4329903f3..d70f91e8a 100644
--- a/lib/pdk/cli.rb
+++ b/lib/pdk/cli.rb
@@ -46,7 +46,23 @@ def self.anonymised_args
     end
   end
 
+  def self.deprecated_runtime?
+    Gem::Version.new(RbConfig::CONFIG['ruby_version']) < Gem::Version.new('2.4.0')
+  end
+
   def self.run(args)
+    if deprecated_runtime?
+      PDK.logger.info(
+        text: _(
+          'Support for Ruby versions older than 2.4 will be dropped in the ' \
+          'future PDK 2.0.0 release. We recommend updating your Ruby ' \
+          'installation to ensure that you can continue using the latest ' \
+          'version of PDK.',
+        ),
+        wrap: true,
+      )
+    end
+
     @args = args
     PDK::Config.analytics_config_interview! unless ENV['PDK_DISABLE_ANALYTICS'] || PDK::Config.analytics_config_exist?
     @base_cmd.run(args)
diff --git a/spec/unit/pdk/cli_spec.rb b/spec/unit/pdk/cli_spec.rb
index e82f7a6c9..275a69c40 100644
--- a/spec/unit/pdk/cli_spec.rb
+++ b/spec/unit/pdk/cli_spec.rb
@@ -1,6 +1,10 @@
 require 'spec_helper'
 require 'pdk/cli'
 
+def deprecated_runtime?
+  Gem::Version.new(RbConfig::CONFIG['ruby_version']) < Gem::Version.new('2.4.0')
+end
+
 describe PDK::CLI do
   context 'when invoking help' do
     it 'outputs basic help' do
@@ -10,6 +14,36 @@
     end
   end
 
+  context 'when invoked by Ruby < 2.4.0', if: deprecated_runtime? do
+    before(:each) do
+      allow($stdout).to receive(:puts)
+    end
+
+    it 'informs the user of the upcoming Ruby deprecation' do
+      expect(logger).to receive(:info).with(
+        text: a_string_matching(%r{ruby versions older than}i),
+        wrap: true,
+      )
+
+      described_class.run([])
+    end
+  end
+
+  context 'when invoked by Ruby >= 2.4.0', unless: deprecated_runtime? do
+    before(:each) do
+      allow($stdout).to receive(:puts)
+    end
+
+    it 'does not inform the user of an upcoming Ruby deprecation' do
+      expect(logger).not_to receive(:info).with(
+        text: a_string_matching(%r{ruby versions older than}i),
+        wrap: true,
+      )
+
+      described_class.run([])
+    end
+  end
+
   context 'analytics opt-out prompt' do
     before(:each) do
       # Temporarily bypass suite-wide analytics disable