Bill Colvin, previously finance director of NHP (Nursing Home Properties), has been lured back to his former employer by the offer of the position of chief executive.
Geoff Mason, Jarvis' company secretary, said the board had anticipated the possibility that Colvin would resign and had already prepared for his departure.
He said: "We've already started the recruitment process. It was a contingency plan. All good companies have contingency plans and we're a good company".
But City observers are concerned that the departure of Colvin, who brought with him a strong track-record outside the company, could damage Jarvis' credibility as it recovers from the collapse in its share price.
Shares reached an all-time high of 787.5p in June 1998, then slumped to a low of 125p earlier this year. This week, the shares were trading at about 180p.
Jarvis' fortunes are closely tied to its largest client, Railtrack. In the two weeks after the Hatfield crash, its share price rose by 40%.
In the past 12 months, Jarvis has lost Andrew Gay, chief of traffic systems, rail projects manager David Anderson and public relations director Keith Lockwood.
One City analyst noted that Jarvis was dominated by the strong personality of chief executive Paris Moayedi, and needed a finance director who could balance his influence.
He said: "In some ways it's an attractive company with a good niche business in education PFI. But it could be hard to attract a decent finance director into a company that's headed by a larger-than-life personality surrounded by enthusiastic supporters."
In the five months since his appointment Colvin has split his time between Jarvis and NHP with the agreement of both companies. NHP has been struggling with debt problems and the difficulties of some of its home operators.
According to Mason, Colvin spent an average of two days a week at Jarvis, and fewer in recent weeks. "He wasn't due to come on board full time until the end of December, and did not have a great input."
Until a new finance director can be recruited, the role is being covered by director of finance Robert Kendall. Kendall has been with Jarvis for several years. Previous finance director Henry Lafferty now heads the group's PFI operations.