We present a detailed dataset of planktonic foraminiferal biohorizons to enhance a biostratigraphy for the eastern equatorial Pacific. Middle Miocene to Pleistocene planktonic foraminiferal biostratigraphy is established using 269 samples from Cores 1H to 40H recovered from Integrated Ocean Drilling Program (IODP) Hole U1338B. In addition to the onboard study of Hole U1338A, a total of 60 biohorizons are recognized with three grades of reliability. Generally, these biohorizons are in agreement with each other and consistent with shipboard magnetostratigraphy, except for several discrepancies that may be caused by ecological diachronous processes. The studied sequence can be correlated with Zone M7 to Subzone PT1b. However, we cannot detect Miocene zones M6, M10, and M12 in this sequence because of discrepancies in some zonal marker biohorizons.