A former Immigration and Naturalization Service official pleaded guilty yesterday in U.S. District Court to accepting payoffs in exchange for aiding more than 100 foreigners, mostly Iranians, with immigration problems.

Maron J. (Babe) Sheehi, 55, of Alexandria, who retired last May as an immigration inspector with the INS headquarters in Washington, also pleaded guilty to income tax evasion in connectin with the payoffs.

Judge Thomas A. Flannery released Sheehi on his personal recognizance and ordered him to appear on Aug. 25 for sentencing. Each charge carries a maximum penalty of five years in jail and a $10,000 fine.

Prosecutors said that individuals who referred foreigners to an immigration consulting service in Arlington operated by Maria V. Carballo, described as Sheehi's former girlfriend, were paid a commission. Carballo, who is not charged in the case, then paid Sheehi for advising her on how to fill out fraudulent immigration papers for permanent residency, labor certification and visa extensions.

Sheehi also referred certain cases prepared by Carballo to specific immigration examiners for processing and contacted employees at the U.S. Department of Labor and at the D.C. Department of Labor to get them to process cases filed by Carballo.

Between December 1978, and November 1979, Sheehi received about $24,000, the prosecutors said. Sheehi did not report nearly $22,000 in income in 1979 and evaded taxes of more than $7,000, prosecutors said.