Mosquito-borne diseases indeed pose significant health threats, particularly in tropical and subtropical regions where favorable conditions for mosquito breeding are prevalent. Conventional insecticides have historically been the primary method of controlling mosquito populations. However, the indiscriminate use of neurotoxic insecticides has led to several adverse consequences including environmental toxicity, harming non-target organisms, disrupting ecosystems, and the development of insecticide resistance in mosquito populations. To address these challenges, there's a growing emphasis on developing alternative mosquito control strategies that are more sustainable and environmentally friendly. In the current study the larvicidal and pupicidal activity of combination of Tridax procumbens leaves extract, Marigold flower waste, and Bacillus thuringiensis (Bt) on Culex species was evaluated. Doses ranging from 10 to 450 ppm were tested for their larval and pupal insecticidal effects on Culex sp. mosquitoes in controlled laboratory and outdoor environments. The LC50 values were determined for extracts from Tridax procumbens leaves and Marigold flowers waste using probit analysis. The combined methanolic plant extracts from Tridax procumbens leaves and Marigold flower debris displayed larvicidal effects, showing the greatest mortality rate with LC50 values of 99.53, 135.1, 249.4 and 370.8 ppm against IInd, IIIrd, IVth larvae instars and pupa respectively. Bacillus thuringiensis (Bt) demonstrated its best activity with LC50 values of 31.62, 51.04, 69.93 and 120.2 ppm against IInd, IIIrd, IVth larvae instars and pupa respectively. However when a combined therapy was given LC50 values were 43.24, 69.61, 204.9 and 274.8 ppm. No mortality was observed in the control. These findings indicate that the methanol extracts derived from Tridax procumbens leaves and Marigold flower waste, along with the use of Bacillus thuringiensis (Bt), holds promise as an environmentally friendly method for managing the malarial vector, Culex sp., a primary target in vector control initiatives. This research represents the initial documentation of the joint larvicidal and pupicidal effectiveness of these plant extracts and bacterial toxin agent against Culex sp. mosquitoes.