Background: Globally unexpected 219 million malaria cases occurred 2021, with 90% of these cases happening in the WHO Africa Region (World Malaria Report, 2021). In the same period, there were unexpected 435,000 malaria transmissions worldwide, with children less than five years being the most-at-risk, representing approximately 61% of malaria infections globally.  Malaria is among the major causes of morbidity and mortality in Kenya and Migori County, representing 16.4% of outpatient attendances (KHIS, 2021). In 2019, IRS coverage 95.4%. This was reason enough to assess contributing factors leading to not reaching targeted 100% of the households mapped despite massive resources.

Methods: The study adopted analytical cross-sectional design. The study area Migori County specifically Awendo, Uriri, Rongo, Suna East, Suna West and Nyatike Sub Counties, where IRS had been implemented in four sessions. The study period was November 2021 to April 2022. The respondents were selected from sampled villages; Migori County was purposively selected because had four sessions. Kenyatta University Ethics Review Committee, Statistical analysis using SPSS 2.6. The sample size determined using Cochran (1963) formulae for a single population of 1000 households.

Results: 249(90%) p-value=0.000 of the residents interviewed confirmed their houses were IRS covered while 32(10%) houses were not sprayed reason they were not informed.

Conclusions: Test of significance, chi-square the arrival of spray operators was significant at (p=0.013,<0.05), therefore the Spray operators arrival time for IRS activities affected residents daily calendar leading to closed doors and unmet target.

Keywords: Indoor residual spray, Spray operators, Households, Horseheads, Eligible structures, Insecticide, Chemical