Essex Mills made his first-class debut for
Essex against the Sri Lankans in the tourist match of 2011 at
Chelmsford. He made his Championship debut against
Leicestershire at
Grace Road in July 2011. His figures in the first-innings were 0–51, but in the second innings, he took 3–48. During the winter of 2011/12, Tymal Mills was named on the England Performance Programme (EPP). He began with training at
Loughborough as well as camps in North Wales and with the Greater Manchester Fire Department. Mills then went to
Potchefstroom,
South Africa for three weeks in November on a specialist fast bowling programme. On Friday 16 December, Mills was a surprise inclusion in the 16 man
England Lions squad. In 2012 Mills took 5 List A wickets and average of 58.60. He performed better in the Championship, taking 14 wickets at an average of 30.35. In 2013, his form in List A cricket improved, as he took ten wickets at an average of 23.30. However, he failed to kick on in the Championship, taking 11 wickets, three less than the previous season. His performances for Essex earned him another place on an England performance programme, and he took six wickets for the Lions on their tour of Sri Lanka.
Sussex In 2014, Mills joined Sussex. He took wickets at an average of 20 in the English T20 competition, and his pace ensured he continued to stand out. He also bowled in the First division of the County Championship for the first time, taking 14 wickets at an average of just below 35. In 2015, he was diagnosed with a congenital back condition and as a result, took time out of playing red-ball cricket. He continued to play T20 cricket and took 19 wickets at an average of 18.84. ==Overseas leagues==