Irish Brook is a 1.71 mi (2.75 km) long first-order tributary to Rice Brook.

[2] Irish Brook rises about 5 miles (8.0 km) west-northwest of Limestone, New York in Cattaraugus County and then flows generally northeast to meet Rice Brook about 3 miles (4.8 km) northwest of Limestone, New York.

Irish Brook drains 1.73 square miles (4.5 km2) of area, receives about 45.2 in/year (115 cm/year) of precipitation, and is about 95.92% forested.