We detected very low frequency earthquakes (VLFEs) by the matched-filter technique and calculated the energy rates of shallow low frequency tremors accompanying VLFEs off the Nicoya Peninsula, Costa Rica. We submitted a paper about slow earthquakes off Costa Rica. The methods of detecting VLFEs and estimating energy rates of tremors are written in a JGR paper (https://doi.org/10.1029/2021JB021706). If you use this data, please cite this paper. Data Set S1: list of detected VLFEs. First column: year, second column: month, third column: day, forth column: hour, fifth column: minute, sixth column: second, seventh column: longitude, eighth column: latitude, ninth column: depth (km), and tenth column: magnitude, eleventh column: duration (s). Times are described in UTC. Data Set S2: list of energy rates of tremors accompanied by VLFEs. First column: year, second column: month, third column: day, forth column: hour, fifth column: minute, sixth column: second, seventh column: longitude, eighth column: latitude, ninth column: depth (km), and tenth column: energy rate (J/s). Times are described in UTC.