Purpose: To demonstrate the ability of a newly constructed coincidence detection spectrometry system to better resolve the 511 keV peak present in a 90Y gamma spectrum due to the internal pair production (IPP) component of 90Y decay by electronically filtering out the bremsstrahlung continuum. Method and Materials: A recently determined low‐uncertainty branching ratio for the IPP component of 90Y decay provides the potential to spectroscopically assay the activity of 90Y by measuring the resulting 511 keV peak. However, the use of a single spectrometer to accomplish this is plagued by the presence of a large bremsstrahlung continuum. In this work, a coincidence detection system was constructed that paired a HPGe detector with a large NaI detector. A series of NIM electronics were tuned to gate the energy signal of the HPGe detector by the coincidence signal. A 90Sr /90Y source was measured for 4 h. The energy spectrum gated by coincidence, the non‐gated energy spectrum, and the energy spectrum gated by random coincidence were all collected concurrently. Environmental background (EBG) (i.e. no source present) was measured for 12 h. Canberra Genie™ 2000 software was used to analyze the spectra. Results: The EBG measured with the gated method was found to be negligible with no counts in the peak area. The EBG of the non‐gated method was subtracted from the non‐gated 90Sr /90Y spectrum. Genie™ 2000 was used to determine the 511 keV peak area and uncertainty. The uncertainty was 1.7% for the gated spectrum and 7.9% for the non‐gated spectrum. Conclusion: The ability of this detection system to electronically filter the bremsstrahlung continuum from the 511 keV peak‐of‐interest has been demonstrated. This method results in a reduced uncertainty in the peak area compared to measurement with a single detector.