French striker Louis Saha looked to have earned the hosts a famous fourth round victory at Goodison Park when he brought a dull tie to life with a 62nd-minute header. But Kalou kept his composure to finish well in the 75th minute and force a replay that keeps alive lacklustre Chelsea's season.
Chelsea, who are trying to sign Liverpool striker Fernando Torres, had arrived on Merseyside with an exceptional FA Cup record. Since suffering a surprise sixth round exit at Barnsley in March 2008, the London club have embarked on a 14-match unbeaten run in the famous competition. Thanks to Kalou, that is now 15 unbeaten.
"It was a difficult match because Everton put a lot of strong pressure on us all the time," Chelsea manager Carlo Ancelotti told ESPN. "We showed good spirit. The second half we didn't play well but the spirit was good."
Everton boss David Moyes said his side were unlucky to have conceded an equaliser at a time when they had started to get on top. "Their goal was against the run of play, we had control in the second half and I thought the boys played well today," Moyes said. "I thought we had more chances in the second half, we were well organised and I didn't think we would concede a goal."
Trailing leaders Manchester United in the Premier League and with Barcelona favourites to win the UEFA Champions League, the FA Cup once again represents Chelsea's most realistic hope of silverware this season. But despite starting with eight players who played in last season's win over Portsmouth in the final at Wembley, Chelsea struggled to stamp their authority on proceedings.
Their travelling fans had to wait until the 31st minute to see Everton keeper Tim Howard make a save, the United States international doing well to keep out Nicolas Anelka's effort after the Frenchman was sent clear by Ramires. By then Everton had twice tested Petr Cech through Jack Rodwell and then Diniyar Bilyaletdinov's firm header.
Yet chances were few and far between on an afternoon when Chelsea fans taunted Everton's Merseyside neighbours Liverpool with chants of "Torres, Torres give us a wave" and "Fernando Torres Chelsea's No 9". Chelsea could certainly have done with Torres's cutting edge at Goodison. Florent Malouda forced Howard into a 35th-minute save with a powerful left-foot drive but there was little threat from Didier Drogba during a first half to forget.
Kalou cancels soaring Saha
Everton upped the tempo after the interval, Saha denied by a fine block by Ramires before Cech tipped Marouane Fellaini's 56th-minute header over the bar. But Saha was not to be denied and, after Leighton Baines had delivered a fine corner, the former Manchester United striker powered an unstoppable header beyond Cech.
However, Everton's lead lasted just 13 minutes as Kalou levelled things up three minutes after coming on with a precision finish on the back of a swift break.