The Norwegian striker travelled to the Netherlands to complete his move from Odds for a reported £600,000, signing a three-year deal with an option for a further year.
Lauritsen will join the Eredivisie club from Odds, alongside team-mate Joshua Kitolano, at the end of July. The Norwegian mid-season transfer window doesn’t open until August with Odds searching for a replacement before he departs.
Aberdeen had a bid of around £300,000 accepted for the 24-year-old who has scored four goals in 11 Eliteserien games so far this season but he has opted for Sparta.
“We were looking for a striker that suited our playing style,” the club’s sporting director Gerard Nijkamp said. “Tobias is a player that we have followed for a long time and has convinced us of his qualities, because he can be of value to Sparta both as a point of contact but also as a goalscorer.
"We knew that there were also clubs in other countries that would like to take him, so we are happy that he chose Sparta.”
The Dons have landed another of their key forward targets with the signing of Bojan Miovski, who has joined on a four-year deal from MTK Budapest for a fee of more than £500,000.
Manager Jim Goodwin is still eyeing further reinforcements in attack with pace a key focus.
"We’re still talking to a number of players,” he said prior to Lauritsen’s move to Sparta Rotterdam. “I think we’re still a little bit short in a few key areas of the team.
“I would still like to add a bit more pace at the top end of the pitch as well, whether that’s in the striking department or out in the wide areas.
“Lauritsen is a name that’s been flung about by a number of people. But we are speaking to so many players that it wouldn’t be fair for me to mention them all. But Lauritsen is a good player.”
Aberdeen have signed five players this summer and head to Spain next week for a warm weather training camp.