The man is said to have approached the women from behind and touched them between their legs or the backside and then left the scene.
Five women reported similar incidents to the police over the weekend, and officers are now investigating other reports of groping from the start of the year in connection with the weekend's incidents.
“We have around 15 reports where we suspect it could be the same perpetrator,” Lisa Sannervik of the Uppsala police told Swedish news agency TT.
On Tuesday police said they had seized a 25-year-old suspect on Monday evening.
Witnesses said they had seen the man getting out of a car, putting on a light blue surgical mask and walking towards a woman at a bus stop, but turning around before reaching her. He was stopped by members of the public who thought he acted suspiciously and police were called to the scene.
Police believe the man is the serial groper they have been looking for.
The incidents over the weekend took place at Stabby Allé, Blåsenhus/Von Kraemersallé, Arosgatan, Rackarbergsgatan and Gamla Upplandsgatan/Vattholmavägen, public broadcaster SVT reported.