This paper addresses national treatment for IP uncertainties (NTIPU) as to whether it is upheld, its changing nature, and differences between patents and trademarks. Based on the institutional theory, empirical evidence in the US and China, the lagged regression modeling of longitudinal data, and multiple comparison, we find that NTIPU is upheld in the past 12 years for trademarks due to equal or favorable treatment for foreigners in granting for both countries, and in pendency for China, but not upheld against pendency due to shorter duration for US locals. Both countries show progress (pendency and foreign granting in China, US granting) or remain unchanged (local granting in China, and US pendency) when compared with pre-2002 eras. Consistently, patents demonstrate shorter pendency but lower granting than trademarks for both countries. The findings address theoretical and empirical voids of NTIPU and provide implications to handle IP uncertainties in bilateral collaboration.