The use of 90° bend is common in pipeline networks to connect the horizontal and vertical pipes in different orientations. The gas-oil-water flow pattern experiences a significant change while flowing through the bend. The centrifugal and gravitational forces influence the upstream flow pattern and transform it into a different type in the downstream pipe. An experimental study is conducted to identify flow pattern transformation in horizontal to vertical upward bend having an (R/d) ratio of 1. Each phase velocity affects the flow patterns; hence, the superficial velocities have been varied in the range of 0.5-5, 0.08-0.36, and 0.08-0.36 m/s for gas, oil, and water, respectively. The three-phase flow patterns in the bend's horizontal and vertical legs have been identified and discussed in detail. Flow regime transition maps are plotted, and the variation in flow patterns with the change in superficial velocities of fluids has been analyzed. The pressure drop has been analyzed, and the prediction model for total pressure drop across the bend has been developed. The comparison of the experimental and predicted results showed close agreement. © 2022 American Chemical Society. All rights reserved.