The 16-year-old was project manager for team Odyssey, who flopped and only managed to get 800 orders for their publication compared to Team Platinum's impressive 7,500.
Maria Doran and David Odhiambo, for a second week in a row, joined Sean in the final boardroom to defend their actions on the task. Lord Sugar was critical of Sean's decision to not bring back Patrick McDowell, who made a hash of the team's third pitch.
Sugar also described the overall team effort as "disastrous to say the least".
Coming to a final conclusion on the firing, he added: "Maria - this is a tough situation for me. I do admire your forcefulness and bubbliness, and on that basis I'm going to let you remain in this process.
"Sean - I think your mistake today was bringing the wrong person back and taking your eye off the ball of what you're supposed to be good at doing. On that basis it is, with regret - you're fired."
Speaking after the show, the teenager said: "Although Lord Sugar fired me today I think I can walk out here with my head held high. I'm going to go home and continue working on all the things that I have coming up. In five or ten years' time I'm going to be successful."
The Young Apprentice continues next Thursday (November 15) at 8pm on BBC One.