Cantrill was born in Vermont, later moving to Colorado, where he attained the rank of Eagle Scout. He studied computer science at Brown University, spending two summers at QNX Software Systems doing kernel development. Upon completing his B.Sc. in 1996, he immediately joined Sun Microsystems to work with Jeff Bonwick in the Solaris Performance Group. In 2005 Bryan Cantrill was named one of the 35 Top Young Innovators by Technology Review, MIT's magazine. Cantrill was included in the TR35 list for his development of DTrace, a function of the OSSolaris 10 that provides a non-invasive means for real-timetracing and diagnosis of software. Sun technologies and technologists, including DTrace and Cantrill, also received an InfoWorld Innovators Award that year. In 2006, "The DTrace trouble-shooting software from Sun was chosen as the Gold winner in Wall Street Journal's 2006 Technology Innovation Awards contest." In 2008, Cantrill, Mike Shapiro and Adam Leventhal were recognized with the USENIXSoftware ToolsUser Group award for "the provision of a significant enabling technology." Together with Shapiro and Leventhal, Cantrill founded Fishworks, a stealth project within Sun Microsystems which produced the Sun Storage 7000 Unified Storage Systems. He left Oracle on July 25, 2010 to become the Vice President of Engineering at Joyent. He announced his transition to being Chief Technology Officer at Joyent in April of 2014, and held that position until announcing his departure as of July 31 of 2019. He was a member of the ACM QueueEditorial Board.
During an online technical discussion of Solaris with Linux kernel developer David S. Miller in 1996, Cantrill responded to Miller's lengthy comment with a one-line reply, "Have you ever kissed a girl?" In 2015, during a discussion concerning Ben Noordhuis's departure from the Node.js project, Cantrill said that the 1996 comment continues to be cited, decades later, and wrote about his regrets in sending the response, which he called "stupid". After Cantrill left Oracle in 2010 he compared the company's behavior to the Nazis'. Cantrill announced at FISL 2012 his strong preference for permissiveopen source softwarelicenses over copyleft licenses by calling the copyleft GPL license family "anti-collaborative" and "viral."