Arsenal went ahead through a 57th-minute Kim Little penalty but Kerr headed an 89th-minute equaliser to ensure Chelsea stay three points clear of the Gunners at the top.
The crowd of 46,811 was the second biggest in WSL history.
There were worrying scenes of crowding outside Emirates Stadium and many supporters only reached their seats after kick-off following huge queues.
Arsenal said in a statement: “Our matchday operation was the same as every other fixture and event at Emirates Stadium.
“An early kick-off combined with a number of new supporters to our stadium, coupled with 50 per cent of supporters arriving in the last 20 minutes before kick-off resulted in busy turnstile areas.
“We will continue to educate supporters on arriving early to the stadium for necessary security and bag checks and continue to discourage supporters bringing any necessary luggage and large bags.”