Barku Sara () is a village in Shirju Posht Rural District of Rudboneh District in Lahijan County, Gilan province, Iran.
At the time of the 2006 National Census, the village's population was 1,645 in 478 households. The following census in 2011 counted 1,451 people in 493 households. The 2016 census measured the population of the village as 1,368 people in 520 households. It was the most populous village in its rural district.