The 31-year-old is currently on international duty at the World Cup, and started Samoa's Pool D games against Namibia and Wales.
He joined Quins from Super League side St Helens at the start of last season, and made a big impression as the London club went on to win the Amlin Challenge Cup.
And director of rugby Conor O'Shea is keen to see Fa'asavalu back in a Quins shirt once his commitments in New Zealand are over.
He said: "Maurie has made a huge impact on both players and supporters alike and his example as a professional in everything he does is one which all young players should follow.
"He is a delight to have around. There is no doubt he brings something different and will help us develop further as a group. We look forward to having him back after the Rugby World Cup."
Fa'asavalu added: "I am really excited to have re-signed with Harlequins, from the end of this season, for another two years.
"It's great to be part of a squad that is continually growing and where everyone is working hard to achieve our goals to bring silverware to the club.
"My family has really settled in down here and we enjoy the lifestyle, and the welcoming and inclusive nature of Harlequins makes it a great all round."
Gilbert has released a new line of rugby cleats. The Gilbert Virtuo 8S is part of the exciting new product. Check it out.
The entire All Blacks apparel line has been updated for 2013/14. Check out the New Zealand All Blacks polo.
The Nike Tiempo is a solid rugby cleat and one of few styles still made from full-grain natural leather.
The Gilbert Blitz 8S rugby cleat is a great cleat at a great price of $69.99. Get a new pair of cleats today.
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Wear the crest of the British and Irish Lions on your t-shirt. A great look for the summer.
The All Blacks Performance t-shirt is black with hints of blue from the training jersey. Very Cool.
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The USA Rugby Pro Alternate rugby jersey is perfect for any fan of the Eagles. Get yours to wear during the summer Test matches.
The NEW All Blacks 2013/14 jersey has arrived at World Rugby Shop. Dare to wear the colors of the All Blacks.