The competitions in Monaco are the first of three competition stops on the annual "swimming tour" Mare Nostrum, with competitions also in Barcelona and Canet.
The 50-meter distances are decided over two days with finals in duel format.
Yesterday, trials, round of 16 and quarterfinals were swum and Sjöström went undefeated through all steps in both 50 meters freestyle and 50 meters butterfly.
The 28-year-old, who competed sparingly during the spring, looked extremely strong and impressed.
Not least with the victory time 24.06 in Saturday's quarter final of 50 freestyle - new world year best.
Notice also in the final
During Sunday's final session, Sjöström once again faced strong times.
The Swede won the final in the 50 butterfly swim in the time of 25.26, a time that she herself has only been faster than this year.
In the final of 50 freestyle, Sarah Sjöström hit with 24.08, only two tenths slower than yesterday's world year best.
The Olympic silver medalist at the distance gave a nice message of form with the World Cup in Budapest less than a month away.
Double podium places for Hansson
Sophie Hansson has also had a strong competition weekend in Monaco.
Yesterday, the 23-year-old was third in 100 breaststroke with 1.07.46.
The winner was Olympic champion Lydia Jacoby from the USA in 1.06.25.
- The times have been good and it feels like I worked my way into the competition.
For every race I have done, I have gotten better results, says Sophie Hansson to SVT Sport.
The duo Hansson and Jacoby were both again in the final tonight then on the double distance.
Hansson finished second behind Jacoby in the 200 breaststroke with a time of 2.26.47.
- The goal is to get as many races as possible in the body before the World Cup.
I'm not super happy with the times, it's a bit from "pers", but not dissatisfied either and it is of course fun with podium places, says Hansson.
Sophie Hansson has studied in the USA for several years and therefore has not swum Mare Nostrum before.
The elimination format of the 50-meter distances means, if you swim several disciplines and well, very many races in a short time.
An unusual format but fun and challenging, says Hansson.
- It is very stressful for the body but at the same time very good training and it is useful to practice recharging and preparing for a new race on short.
Sophie Hansson was also second today in the final of the 50 meter breaststroke in the time 30.93.
She will continue to compete in Barcelona this week, then awaits the final preparations for the long-distance World Cup in Budapest.
- I hope that my form will peak in 3.5 weeks so after this my topping starts and then we will hopefully grind a little on the times at the WC.