A woman in her 20s was pushed to the ground and assaulted by a man on a bike on Boundary Road near Bournemouth University's Talbot campus on Thursday.
Dorset Police said they believe it could be linked to two attempted sexual assaults on women in September.
Thursday's attacker is described as white and in his late 20s or early 30s.
Officers said he was approximately 5ft 7in (1.7m), of slight to medium build with short dark hair and wearing a black thigh-length coat and dark trousers.
The victim was walking down a footpath at about 21:40 GMT when the cyclist approached and then assaulted her.
The attacker was riding a dark-coloured mountain bike with silver handle bars and rode off towards Columbia Road after the assault.
Det Ch Insp Sarah Derbyshire said it could be linked to the attempted assaults of women on 13 and 14 September at Boundary Road and Slades Farm.
She is appealing for witnesses.

Frimley Health NHS Foundation Trust has 285 full-time vacancies across three sites, which cover Surrey and Berkshire.
The high cost of living in the south of England is said to be a factor affecting recruitment.
Each successful applicant will receive a maximum of £1,340 in subsidies.
Nurses will be offered accommodation at Wexham Park Hospital in Slough, Frimley Park near Camberley and Heatherwood Hospital in Ascot.
Marko Novosil moved from Croatia to become a nurse at Wexham Park after hearing about the incentive.
"The crucial thing for coming here was the support. I realised that when I started I would get the free accommodation which helped me settle in", he said.
Wexham Park Hospital matron Helen Noakes said: "Rental prices are higher in this area, which means people do struggle and the one thing that we can offer people is the free accommodation when they start.
"Longer term we would look to help them find somewhere in the local area to live."
Currently the average monthly rent for a one-bedroom property in Slough is £897, whereas the average for the same sort of property in Camberley is £930.
The average cost for a room in both areas ranges from £500 to £550.

The Paris St-Germain striker scored twice against Portugal on Tuesday but Cristiano Ronaldo's hat-trick took his side through 4-2 on aggregate.
Ibrahimovic, 32, said: "It was probably the last attempt to reach the World Cup with the national team for me.
"A World Cup without me is nothing to watch so it is not worthwhile to wait for the World Cup."
The play-off between Sweden and Portugal, who had both finished second in their qualifying groups, had been billed as a showdown between Ibrahimovic and Ronaldo - two of the best players in the world.
At the age of 32, Sweden skipper Zlatan Ibrahimovic may not have another opportunity to play in a World Cup finals.
And the tournament would represent a nadir in the Paris St-Germain striker's career. He has never scored at a finals having made two substitute appearances in 2002 and three starts in 2006.
They ended up scoring all six goals between them as Portugal won 4-2 on aggregate.
Former Inter Milan forward Ibrahimovic, who has played in two World Cups, scored eight times in qualifying, including the play-offs, and assisted another six goals - having a hand in 14 out of Sweden's 21 goals.
He told Uefa's website: "Why did we lose? To be honest, they were better than us. We should be proud. We couldn't have done better than we did.
"Of course, we could look back at our mistakes, but these things happen. They punished our mistakes. After making it 2-1 it felt like we were on a roll, our hopes grew, but unfortunately they made it 2-2 soon afterwards."
Real Madrid forward Ronaldo, who has scored 34 goals in 24 games this season for club and country, said: "I just did my job, as I have been doing lately. I always try to give my best - that is always my goal."
He is now Portugal's joint-top scorer, along with retired former Paris St-Germain striker Pauleta on 47.
"It was not a priority for me to break Pauleta's record," the 28-year-old said. "I knew Portugal needed me and I stuck to the task at hand. Now we have some time to rest and to do our best for our clubs before starting to think about the World Cup finals."
A sex attack on woman near a university campus could be linked to two other attempted assaults, investigators have said.
[NEXT_CONCEPT]
Nursing job applicants are being offered two months free accommodation in a bid to quell staff shortages at a hospital trust.
[NEXT_CONCEPT]
Sweden captain Zlatan Ibrahimovic says the World Cup is not worth watching without him after their play-off loss.