Aim: This was an in vitro study done to evaluate the change in flexural modulus of flexible denture base material kept in water, denture cleanser, artificial saliva, and open air for different time intervals. Materials and methods: The experimental design included four main groups, with each group having three subgroups. A total of 120 specimens were fabricated with each group containing 30 specimens; these four groups, based on duration in the storage condition, were further subdivided into three groups. Group A1: 15 days, group A2: 30 days, and group A3: 60 days. Results: Flexural modulus of flexible denture in 15 days was found to be highest with denture-cleansing tablet (1246.52 ± 8.69 MPa) and lowest in water (1170.54 ± 7.35 MPa). Flexural modulus of flexible denture in 30 days was found to be highest with open air (1282.94 ± 8.35 MPa) and lowest in denturecleansing tablet (1145.60 ± 5.34 MPa). Flexural modulus of flexible denture in 60 days was found to be highest with open air (1360.34 ± 8.02 MPa) and lowest in denture-cleansing tablet (1120.43 ± 6.34 MPa). Conclusion: According to our study, flexibility of nylon denture base material decreases when kept in open air and water for prolonged period. Initially, flexibility of nylon denture base material increases in denture-cleansing tablet and in artificial saliva, and later flexibility decreased in the first month, then there was not much effect. The best medium for storage of flexible denture was found to be artificial saliva.