Jennings was selected as the County Championship player of the year by the Cricket Writers' Club, and joined the England Lions tour to the United Arab Emirates.

Following his impressive form for Durham, and scoring a century on tour for the Lions, Jennings was called up to the senior England squad for the first time.

[9] He had the highest run total of any batsman in the 2022 County Championship Division One [10] and won the Fans Player of the Season award.

[15] On 22 April 2023, Jennings would suffer a hamstring injury while batting in a County Championship match against Somerset at Taunton and was forced to retire hurt on 189*.

[18][19] In November 2016, Jennings was named in England's Test squad for the final two matches of their series against India to replace the injured Haseeb Hameed.

However, after averaging 15.88 in this series, he was dropped for the first test against West Indies in August 2017, with his place being taken by his former opening partner at Durham, Mark Stoneman.

[25] After the Lord's Test against Pakistan in May 2018, Jennings was recalled in place of Stoneman due to his good form for Lancashire in the County Championship.

Though he had a struggled against India in the previously concluded home series, Jennings was included as part of the team touring Sri Lanka in October 2018.

[26] Jennings also played a crucial role in the field as part of England's victory in the third and final Test, taking four catches at short leg in Sri Lanka's first innings to restrict them to a total of 240.

[28][29] On 17 June 2020, Jennings was included in England's 30-man squad to start training behind closed doors for the Test series against the West Indies.