Bemisia tabaci (Gennadius) (Hemiptera: Aleyrodidae) is a destructive pest that causes significant damage on important agricultural crops through direct feeding, honeydew excretion and plant virus transmission. Chemical control is among the most widely used methods to suppress whitefly infestations but management efforts have become very challenging due to the development of insecticide resistance. This study was conducted to monitor insecticide resistance and detect endosymbiont composition in greenhouse-collected B. tabaci populations from Mersin, Turkey. All greenhouse-collected populations were identified as Middle East-Asia Minor 1 (MEAM-1). Based on Resistance ratios (RRs) of LC50 values, all greenhouse-collected populations were low to moderately resistant to the three neonicotinoids when compared to the reference population. Resistance ratios were in the range of 3.63-8.79-fold for acetamiprid; 7.29-15.29-fold for imidacloprid and 9.74-11.79-fold for thiamethoxam after 72 h of exposure. No or very low levels of resistance (RR <= 2.00) were detected for spinetoram, spinosad and sulfoxaflor. Spinetoram was the most toxic of all the other tested insecticides against all populations. Generally, LC90 values obtained for greenhouse-collected populations were much higher than the recommended concentrations of the neonicotinoids but lower for spinetoram, spinosad and sulfoxaflor. Molecular analysis of endosymbionts indicated that all populations were infected with Portiera and Hamiltonella, whereas only two out of five greenhouse-collected populations were infected with Rickettsia. The insecticide-susceptible lab strain had relatively the highest rate of Rickettsia infections. Moreover, a statistically significant negative correlation was detected between LC50 values and the rate of Rickettsia infections for imidacloprid and thiamethoxam (R = -0.930 and R = -0.866, respectively), while the relationship was non-significant for acetamiprid resistance (R = -0.598).