diff --git a/activerecord/CHANGELOG.md b/activerecord/CHANGELOG.md
index d2bece5303f..a3913c69619 100644
--- a/activerecord/CHANGELOG.md
+++ b/activerecord/CHANGELOG.md
@@ -1,3 +1,9 @@
+*   Use SQLite `IMMEDIATE` transactions when possible.
+
+    Transactions run against the SQLite3 adapter default to IMMEDIATE mode to improve concurrency support and avoid busy exceptions.
+
+    *Stephen Margheim*
+
 *   Raise specific exception when a connection is not defined.
 
      The new `ConnectionNotDefined` exception provides connection name, shard and role accessors indicating the details of the connection that was requested.
diff --git a/activerecord/lib/active_record/connection_adapters/abstract/database_statements.rb b/activerecord/lib/active_record/connection_adapters/abstract/database_statements.rb
index 29d6ae01af5..1ceaa588430 100644
--- a/activerecord/lib/active_record/connection_adapters/abstract/database_statements.rb
+++ b/activerecord/lib/active_record/connection_adapters/abstract/database_statements.rb
@@ -411,6 +411,14 @@ module ActiveRecord
       # Begins the transaction (and turns off auto-committing).
       def begin_db_transaction()    end
 
+      def begin_deferred_transaction(isolation_level = nil) # :nodoc:
+        if isolation_level
+          begin_isolated_db_transaction(isolation_level)
+        else
+          begin_db_transaction
+        end
+      end
+
       def transaction_isolation_levels
         {
           read_uncommitted: "READ UNCOMMITTED",
diff --git a/activerecord/lib/active_record/connection_adapters/abstract/transaction.rb b/activerecord/lib/active_record/connection_adapters/abstract/transaction.rb
index fbf142d89e9..87b40ad40cc 100644
--- a/activerecord/lib/active_record/connection_adapters/abstract/transaction.rb
+++ b/activerecord/lib/active_record/connection_adapters/abstract/transaction.rb
@@ -448,10 +448,14 @@ module ActiveRecord
     # = Active Record Real \Transaction
     class RealTransaction < Transaction
       def materialize!
-        if isolation_level
-          connection.begin_isolated_db_transaction(isolation_level)
+        if joinable?
+          if isolation_level
+            connection.begin_isolated_db_transaction(isolation_level)
+          else
+            connection.begin_db_transaction
+          end
         else
-          connection.begin_db_transaction
+          connection.begin_deferred_transaction(isolation_level)
         end
 
         super
diff --git a/activerecord/lib/active_record/connection_adapters/sqlite3/database_statements.rb b/activerecord/lib/active_record/connection_adapters/sqlite3/database_statements.rb
index 3cd1b8b47e6..c4cae471bbe 100644
--- a/activerecord/lib/active_record/connection_adapters/sqlite3/database_statements.rb
+++ b/activerecord/lib/active_record/connection_adapters/sqlite3/database_statements.rb
@@ -65,25 +65,16 @@ module ActiveRecord
         end
         alias :exec_update :exec_delete
 
-        def begin_isolated_db_transaction(isolation) # :nodoc:
-          raise TransactionIsolationError, "SQLite3 only supports the `read_uncommitted` transaction isolation level" if isolation != :read_uncommitted
-          raise StandardError, "You need to enable the shared-cache mode in SQLite mode before attempting to change the transaction isolation level" unless shared_cache?
+        def begin_deferred_transaction(isolation = nil) # :nodoc:
+          internal_begin_transaction(:deferred, isolation)
+        end
 
-          with_raw_connection(allow_retry: true, materialize_transactions: false) do |conn|
-            ActiveSupport::IsolatedExecutionState[:active_record_read_uncommitted] = conn.get_first_value("PRAGMA read_uncommitted")
-            conn.read_uncommitted = true
-            begin_db_transaction
-          end
+        def begin_isolated_db_transaction(isolation) # :nodoc:
+          internal_begin_transaction(:deferred, isolation)
         end
 
         def begin_db_transaction # :nodoc:
-          log("begin transaction", "TRANSACTION") do
-            with_raw_connection(allow_retry: true, materialize_transactions: false) do |conn|
-              result = conn.transaction
-              verified!
-              result
-            end
-          end
+          internal_begin_transaction(:immediate, nil)
         end
 
         def commit_db_transaction # :nodoc:
@@ -114,6 +105,25 @@ module ActiveRecord
         end
 
         private
+          def internal_begin_transaction(mode, isolation)
+            if isolation
+              raise TransactionIsolationError, "SQLite3 only supports the `read_uncommitted` transaction isolation level" if isolation != :read_uncommitted
+              raise StandardError, "You need to enable the shared-cache mode in SQLite mode before attempting to change the transaction isolation level" unless shared_cache?
+            end
+
+            log("begin #{mode} transaction", "TRANSACTION") do
+              with_raw_connection(allow_retry: true, materialize_transactions: false) do |conn|
+                if isolation
+                  ActiveSupport::IsolatedExecutionState[:active_record_read_uncommitted] = conn.get_first_value("PRAGMA read_uncommitted")
+                  conn.read_uncommitted = true
+                end
+                result = conn.transaction(mode)
+                verified!
+                result
+              end
+            end
+          end
+
           def raw_execute(sql, name, async: false, allow_retry: false, materialize_transactions: false)
             log(sql, name, async: async) do |notification_payload|
               with_raw_connection(allow_retry: allow_retry, materialize_transactions: materialize_transactions) do |conn|
diff --git a/activerecord/lib/active_record/connection_adapters/sqlite3_adapter.rb b/activerecord/lib/active_record/connection_adapters/sqlite3_adapter.rb
index 540a192fd00..98c81d77a1b 100644
--- a/activerecord/lib/active_record/connection_adapters/sqlite3_adapter.rb
+++ b/activerecord/lib/active_record/connection_adapters/sqlite3_adapter.rb
@@ -120,7 +120,11 @@ module ActiveRecord
         end
 
         @config[:strict] = ConnectionAdapters::SQLite3Adapter.strict_strings_by_default unless @config.key?(:strict)
-        @connection_parameters = @config.merge(database: @config[:database].to_s, results_as_hash: true)
+        @connection_parameters = @config.merge(
+          database: @config[:database].to_s,
+          results_as_hash: true,
+          default_transaction_mode: :immediate,
+        )
         @use_insert_returning = @config.key?(:insert_returning) ? self.class.type_cast_config_to_boolean(@config[:insert_returning]) : true
       end
 
diff --git a/activerecord/test/cases/locking_test.rb b/activerecord/test/cases/locking_test.rb
index f597ed525f7..96a2243e445 100644
--- a/activerecord/test/cases/locking_test.rb
+++ b/activerecord/test/cases/locking_test.rb
@@ -798,7 +798,7 @@ class PessimisticLockingTest < ActiveRecord::TestCase
 
         a = Thread.new do
           t0 = Time.now
-          Person.transaction do
+          Person.transaction(joinable: false) do
             yield
             b_wakeup.set
             a_wakeup.wait
diff --git a/activerecord/test/cases/transactions_test.rb b/activerecord/test/cases/transactions_test.rb
index cbdf7319d05..66fa2b9db7d 100644
--- a/activerecord/test/cases/transactions_test.rb
+++ b/activerecord/test/cases/transactions_test.rb
@@ -1386,6 +1386,12 @@ class TransactionTest < ActiveRecord::TestCase
         Topic.reset_column_information
       end
     end
+
+    def test_sqlite_default_transaction_mode_is_immediate
+      assert_queries_match(/BEGIN IMMEDIATE TRANSACTION/i, include_schema: false) do
+        Topic.transaction { Topic.lease_connection.materialize_transactions }
+      end
+    end
   end
 
   def test_transactions_state_from_rollback