Lennon was born in Bellshill and raised in Blantyre, South Lanarkshire, the daughter of Gerard Ward, a council health and safety manager, and his wife Helen.

[4] Shortly after being elected she was appointed by leader Kezia Dugdale as Shadow Minister for Inequalities, a role in which she campaigned to raise awareness about the need for women to check themselves for signs of breast cancer.

[5] In the 2017 Scottish Labour leadership election, Lennon nominated fellow Central Scotland MSP and left-wing ally Richard Leonard.

Lennon asked Nicola Sturgeon to take urgent action to review suicide prevention procedures in NHS Lanarkshire.

[9] In an October 2018 Shadow Cabinet reshuffle, Lennon was again promoted to Spokesperson for Health and Sport, replacing Richard Leonard's former leadership rival Anas Sarwar.

[12][13] Along with Neil Findlay, Lennon abstained on an SNP government bill in favour of a second Scottish independence referendum.

[15] During the campaign, Lennon said she would not oppose a second Scottish independence referendum although would argue for an alternative Devo Max option.

[26] Lennon was one of 5 Labour MSPs who was absent for a Scottish Parliament vote calling for the UK Government to reverse its decision to means-test the Winter Fuel Payment.