Will they be able to continue their success into 2016?
Players coming in
Chelsea showed their intention with their biggest signing of the transfer window, Karen Carney. She was a well loved and crucial player in her time at Birmingham City and has been a great player as part of the England team.
Carney, who can play as a winger or as a number 10, will be able to help create goals and supply the likes of Ji So-yun, Eni Aluko and Fran Kirby with plenty of chances. She can also score goals, with 26 in her England career and 12 in her latest stint with Birmingham.
There were also a few other players brought in. Becky Spencer, also from Birmingham, was recruited as a back-up goalkeeper. This means that Chelsea have plenty of options in case of injuries or international duties. They also have Fran Kitching in the team.
Bethany England and Jade Bailey were also signed, both young and able to add to the plenty of options in attack. England was from newly promoted Doncaster Belles, with whom she excelled last year, whilst Bailey arrived from Arsenal.
There are also quite a few players that have left on loan, mainly youngsters for experience. The trio of Millie Farrow, Jodie Brett and Rosella Ayane have gone on loan to Bristol City in order to strengthen the side and help gain promotion. Laura Coombs has moved on loan to Liverpool too after they lost many players.
There were some permanent departures too. Marie Hourihan left and joined last year's title rivals Manchester City; Marija Banusic went back to Sweden to join Eskilstuna United; Jenna Dear has gone to Everton and Atlanta Primus has gone to Yeovil Town.
Nonetheless, when considering the roles of these players in the team last season and those recruited ahead of the 2016 campaign, the departures do not weaken Chelsea.
The Blues have done fairly well in pre-season.
They were then held to a goalless draw against Pitea IF, but rounded off their pre season with a 7-1 thrashing of a Bristol City side fielding many Chelsea loanees.
One to watch
Despite all the signings, Fran Kirby is the one to watch. This will be her first full season with Chelsea after having joined after the 2015 FIFA Women's World Cup.
She did well last season, netting four goals in five league games, and is a nightmare for defenders with her dribbling ability. She has shown just how much she has grown in her confidence and in her game in pre season too. She has netted four goals in the build up to the new campaign, as well as notching two assists against Bristol.
She will be crucial to Chelsea keeping their title, with the amount of goals she will score and also help create.
Having strengthened an already strong side, Chelsea look to be the side to beat. Every team will be wanting to try to beat them but they will have to be solid at the back and clinical at the front.
They also have their FA Women's Cup title to defend. Their first match will be against newly promoted Doncaster on Sunday, which will definitely be an interesting one. The Belles won't be a walkover but Chelsea are the favourites.
The double was done last season but could there be a treble or quadraple on the cards? Chelsea will also be in the WSL Cup (which they were knocked out of last season) and the Champions League.
Either way, this season will be an exciting but nervy one for the team and fans alike, with plenty of promise but plenty at stake.