Salinization is a major global issue due to its adverse impact on agricultural productivity and sustainability. A substantial part of the coastal region of Bangladesh is affected by different magnitudes of salinity. Therefore, maintaining sustainable agricultural production is a major emphasis for policymakers. The objective of this study was to assess the salinity tolerance threshold for Boro season rice cultivation in the southwestern coastal areas of Bangladesh based on farmers’ perceptions of salinity problem. We applied an adaptation tipping point (ATP) approach that signifies the points, e.g., timeframe, when the threshold of a system is reached and alternate strategies must be considered for management planning. The primary data were collected through household surveys and focus group discussions, and were then interpreted and harmonized with literature reviews and expert opinions. The results revealed that farmers perceived the panicle emergence stage of rice as the most vulnerable to salinity and that a high salt concentration in the soil during this growth stage results in a lower yield. In southwestern Bangladesh, panicle emergence of rice during the Boro season is usually observed from March to April, the same period when salinity reaches its peak level. Based on farmers’ perspectives of salinity problems and literature, this study defined the salinity tolerance threshold between 4–5 dS/m for traditional Boro season rice varieties and between 8–10 dS/m for newly released salt-tolerant rice varieties. We conclude that for the traditional Boro season rice varieties the tipping points might already have been reached in some coastal areas of southwestern Bangladesh, while for newly released salt-tolerant rice varieties these tipping points could be reached in the near future.