The Finn joined the Silver Arrows for the start of the 2017 campaign, taking over from Nico Rosberg who surprised many when he opted to retire from the sport on the back of his world title win in 2016.
The hope for the former Williams man, then, was to try and replicate that and take the fight to Lewis Hamilton but, of course, we stand here now knowing that he couldn't quite edge the Briton in the years to follow.
Hamilton has described Bottas as his best teammate ever, owing in part to the fact that Mercedes have been so harmonious with him around, but all things come to an end and he'll be replaced by George Russell for 2022.
What are Bottas' most defining moments in an up and down time at Mercedes, though? We take a look at 5...
First win in Russia
This was a fine moment in Bottas' early Mercedes career as he achieved his first F1 victory and obviously first for the Mercs as well.
It was great to see him become the 107th race-winner in the history of the sport and he would have hoped that that experienced would have kicked him on to higher heights - though a title challenge would never materialise.
Bottas described himself as Bottas 2.0 ahead of the 2019 season and kicked it off in fine style with a good win at Albert Park, streaking away from the field.
There was obviously hopes that this would mean he'd be now ready to take a title fight to Lewis Hamilton but, again, momentum never kept with him and eventually he'd be adrift of the Briton who would seal his sixth crown.
Bottas again won the opening race of the season in 2020 and the hope would have, again, been that he would take the fight to Hamilton with Mercedes easily the team to beat last year.
However, the title challenge would unfortunately peter out pretty quickly to leave the Finn once again having to settle with a fight for second in the Drivers' standings and helping the Silver Arrows with a Constructors' championship. These victories summed Bottas' Mercedes career up in that he could achieve race wins but not regularly enough to win a championship.
This season has perhaps seen more mistakes creep in from Bottas and we saw that dramatically at Imola as he and George Russell, of all people, came together in a big, high-speed shunt.
The two exchanged unpleasantries after the crash and this was perhaps the beginning of the end for Bottas at Mercedes, just with the confidence that seemed to sap from him as so many headlines were written.
We again saw Bottas in trouble with him causing a shunt at the beginning of the Hungarian Grand Prix that saw several retire and also ruined the race of Max Verstappen, who suffered serious damage.
It was an incident that the Finn would not have been proud of, of course, and with Russell's continued performances a switch between them now makes sense.
Valtteri has been a solid driver in the main, though, with good pace to help deliver Mercedes' run of Constructors' titles - it'll be fascinating to watch what he does with Alfa Romeo next year.News Now - Sport News