In a career that has spanned over four decades, he has scored numerous films including The Player (1992), The Shawshank Redemption (1994), Meet Joe Black (1998), American Beauty and The Green Mile (both 1999), Pay It Forward (2000), In the Bedroom (2001), Road to Perdition and White Oleander (both 2002), Finding Nemo (2003) and its sequel Finding Dory (2016), Lemony Snicket's A Series of Unfortunate Events (2004), Cinderella Man (2005), WALL-E (2008), the James Bond films Skyfall (2012) and Spectre (2015), Bridge of Spies (2015), 1917 (2019), and Elemental (2023).

[5] Lionel, who succeeded Alfred as music director for 20th Century Fox, gave Thomas his first scoring assignment on a 1979 episode of the series The Paper Chase.

[6] In 1983, John Williams, who was a friend of both Alfred and Lionel, invited Newman to work on Return of the Jedi, orchestrating the scene in which Darth Vader dies.

Newman said that he thought "it was a tough job, at first" for requiring him to "develop vocabularies and a sense of procedure", only getting comfortable with writing scores "and not fraudulent in my efforts" after eight years.

Newman believed the score helped move the film along without disturbing the "moral ambiguity" of the script, saying "It was a real delicate balancing act in terms of what music worked to preserve that.".

His critical and commercial success continued in the years to follow, which included scores for films directed by celebrated independent filmmakers such as Steven Soderbergh (Erin Brockovich), and Todd Field (In the Bedroom).

He was nominated consecutively for a further three Academy Awards, for Road to Perdition (2002; his second collaboration with Sam Mendes), Finding Nemo (2003), and Lemony Snicket's A Series of Unfortunate Events (2004).

However, he lost on each occasion, to Elliot Goldenthal (for Frida), Howard Shore (for The Lord of the Rings: The Return of the King), and Jan A. P. Kaczmarek (for Finding Neverland).

The latter score was very well received by film music critics, earning Newman BAFTA and Oscar nominations for the second consecutive year, both of which he lost to Steven Price for Gravity.

[12] Also that year, Newman returned to score the 24th James Bond movie Spectre, the sequel to Skyfall and a continuation of his longtime collaboration with Sam Mendes.

He is also fond of incorporating unusual instruments such as the zither, hurdy-gurdy, psaltery and hammered dulcimer,[6] or unexpected sounds, like Aboriginal chants and the chirping of cicadas.