Chelsea currently have Zecira Musovic, Ann-Katrin Berger and youngster Emily Orman in their squad as first-team goalkeepers.
The Blues lost the Continental League Cup final to Arsenal at Selhurst Park on Sunday but they remain in contention for the Women’s Super League title, where they are four points behind leaders Manchester United with two games in hand.
Evrard, 27, impressed at the Euros in England last summer, where she helped Belgium reach the quarter-finals and kept a clean-sheet against Italy in the group stage.
She will arrive at Kingsmeadow following the end of the Belgian Women’s Super League season, where current club Leuven are league leaders. Evrard has conceded just seven goals in 20 games for the club so far this campaign.
Evrard said: “It’s really crazy, dreams do come true. I’m really happy, excited and honoured to play for a big club like Chelsea. I follow the women’s games, I watch the competition in England, and it’s always fun to watch the Chelsea games.
“I hope to bring my performance from the Euros to here,” she added. “The big goal is to bring something to the team. Chelsea want to win trophies, that is also my ambition and I want to win a lot at the club.’
Manager Emma Hayes was delighted to get the deal over the line and said: “Nicky will be a great addition to our squad, certainly she showed her quality and her talent in the Euros last summer. Coming into a full-time, professional environment will certainly help her take the steps in the next direction. I know she will complement Ann and Zecira and add to our goalkeeping union.”
Evrard made her Belgium national team debut in 2013 and has since won 61 caps. She conceded six goals in her last outing, when the Lionesses beat Belgium 6–1 at Bristol City’s Ashton Gate a fortnight ago to successfully defend their Arnold Clark Crown from last year.