This study was carried out to estimate the microplastics (i.e. plastics measuring less than 5mm, reported in unit of pieces/m^3) concentration in the Bay of Bengal and South Pacific Ocean. Microplastics data was collected from 2013-05-27 to 2015-11-04. The Bay of Bengal expedition was aboard SV Mir while the South Pacific Ocean expedition was aboard RV Cabo de Hornos. During the two expeditions, the study investigated whether the microplastics sampling instruments, the new, high-speed AVANI trawl (All-purpose Velocity Accelerated Net Instrument) collected similar amounts and types of microplastics as two established scientific trawl designs, the manta trawl and the neuston net. The AVANI trawl can collect microplastics from the sea surface at relatively higher speeds up to 8 knots and during long transits (allowing for a nearly continuous sampling effort over long distances), whereas the manta and neuston trawls must be towed slowly in a less turbulent sea state and often represent shorter tow lengths. This dataset contains the results from all 36 sampling stations in the Bay of Bengal and 52 sampling stations in the South Pacific Ocean, in a spreadsheet format.