The FCO advised against all but essential visits following the June 2015 beach attack in which 30 Britons were killed.
However, this guidance was withdrawn for the majority of the North African country last year.
Thomas Cook resumed holiday sales to UK customers in August, with trips beginning today.
The company did not stop selling trips to French, German and Belgian holidaymakers after the Sousse attack as their governments did not recommend that their citizens should not visit Tunisia.
Operator Thomas Cook have resumed flights to Tunisia for the first time since the Sousse massacre
Thomas Cook had only stopped flights from the UK and not other western european countries
Some 440,000 people from the UK visited Tunisia in 2014, according to the Office for National Statistics.
Demand was reportedly even higher during the following year, until the Sousse attack in which gunman Seifeddine Rezgui killed a total of 38 tourists.
Terror group Islamic State claimed responsibility.