Barry will head Precept's project advisory services group, which will advise on cost and dispute resolution. Precept split into three divisions (the other two being project management and decision support) last October.
Barry said he was sad to leave EC Harris but was attracted by Precept's ambition. He said: "The expertise and entrepreneurial spirit within Precept was frankly irresistible."
EC Harris chairman Richard Clare said he wished Barry well.
Precept director David Barry (no relation to Paul) said Barry would help the firm grow further. He said: "The recruitment of someone of Paul's experience and reputation both supports this (growth) initiative and expands our service capability considerably."
Precept, which now has a staff of 40, was founded by David Barry, former European head of US project management firm O'Brien Kreitzberg, and Brian Norton in 1998. It has offices in London, Stirling and Glasgow and plans to open an office in Manchester later this year.