Pressley will concentrate on his job as assistant boss at Falkirk.
“I have thoroughly enjoyed my time with Scotland and I am extremely grateful for the opportunity,” he said.
“It has been an honour to be involved with the national team.
“It was evident from the outset that my role in team affairs would be minimal and that my opportunity to do any coaching would always be limited in the current management structure.
“Although I appreciate the benefits for a young coach of being involved in an international set-up, after 18 months in the role I felt that it was the right time to step back from Scotland and concentrate all my efforts on my club career.
“I would like to thank George for the experience and I would also like to wish the team every success for the future.”