Tomkins was born into a musical family. His father, also named Thomas, was a vicar-choral of the Cathedral of St. David's, and his siblings became, variously, a composer (John), an organist (Giles) and a consort musician (Robert). He was, like Robert Morley, a student of Byrd and his master's style of music continued to influence his music all his life. Around 1596, he succeeded Nathaniel Patrick as organist to Worcester Cathedral, a post that he retained for most of his life. By 1620, he was full member of the Chapel Royal, and it appears that he divided his time between Worcester and London. In 1621, he became organist to the Chapel Royal, a very prestigious post, which he held jointly with Orlando Gibbons. He was nominated for the position of Composer of the Kings Music in 1628, but lost out to Alfonso Ferrabosco.
After 1628, he appears to have spent more time in Worcester. With the pre-civil war unrest, clashes between the radical Worcesterians and the more conservative Cathedral clergy grew nasty. Upon the outbreak of active civil war, roundheads attached the Cathedral and the organ dismantled in 1646. Tomkins, however, stayed in Worcester near the cathedral for another eight years before moving to the town of Martin Hussingtree, where his son Nathaniel lived. He died two years later.
Tomkins was the last of the school of English composers in the mold of Byrd. He continued to write in this style long after it was outdated and (relatively) unfashionable. His great collection of madrigals, for example, was his Songs of 3, 4, 5, and 6 Parts published in 1622. This collection comprised madrigals of a surprisingly outdated style, all of them belonging to the era prima prattica rather than the newer seconda. His large number of anthems fared somewhat better. His instrumental music, while also old-fashioned for the time, is compositionally sound and contains some very inventive work.
This clinging to older practices perhaps accounts for Tomkins' rather confused position in music history. Some scholars praise him as a genius. Some damn him as a dilettante. The truth, however, lies between these two extremes. He was simply a talented, if highly conservative composer, who wrote in a style that obviously pleased himself rather than the dictates of fashion.