He was a Fellow of the Society of Antiquaries of London and in 1768 was elected a Fellow of the Royal Society as a "Rector of Buckland in Hertfordshire, Author of the Greek Thesaurus lately published, and Fellow of the Society of Antiquaries of London, a Gentleman well skilled in Natural History and every branch of Polite Literature". 
He was appointed Garrison Chaplain at Portsmouth barracks in 1775.
Morell wrote the longest and most detailed surviving account of collaboration with Handel.
He died in 1784 and was buried in Chiswick, London.
He is best known as the librettist of the following of George Frideric Handel's oratorios:
- Judas Maccabaeus (1747).
- Joshua (1747).
- Alexander Balus (1748).
- Theodora (1750).
- The Choice of Hercules (1750). Uncertain if Morell was the librettist.
- Jephtha (1752).
- The Triumph of Time and Truth (1757). Morell was probably the librettist.
- Morell, Thomas. "Morell, Thomas (1703–1784), classical scholar and librettist | Oxford Dictionary of National Biography". Oxforddnb.com. Retrieved 2020-03-01.
- Smith, R. (2002). Thomas Morell and His Letter about Handel. Journal of the Royal Musical Association, 127(2), 191-225. Retrieved March 1, 2020
- "Portrait of Thomas Morell | Royal Society Picture Library". Pictures.royalsociety.org. 2012-05-15. Retrieved 2020-03-01.
- "Morell; Thomas (1703 - 1784) - DServe Archive Persons Show". Collections.royalsociety.org. Retrieved 2020-03-01.
- "Library and Archive Catalogue". Royal Society. Retrieved 2020-03-01.
- The Manuscripts of J. Eliot Hodgkin, F.S.A., of Richmond, Surrey, Historical Manuscripts Commission 15th Report, Appendix, pt ii (London, 1897), 91-93
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