Starch nanocrystals (SNC) are insoluble platelets with crystalline structures produced by acid hydrolysis. Pretreatments, including heat–moisture treatment (HMT), annealing (ANN), and sonication (SNT) can be used to improve SNC properties. They investigate the impact of these pretreatments on SNC structure and properties, including hydrolysis kinetics and yield, molecular structure, infrared spectroscopy, crystallinity (Xc), and thermal stability. Hydrolysis of native and pretreated starches followed a two-phase first-order model with an initial rapid stage and a slower second stage based on the k-values. SNC yield is improved by at least 180% than previously reported. HMT SNC yield is 42.3% while native SNC is 35.2%. Structural analysis reveals that SNC displayed an A-type structure with increased X_c. However, prolonged acid hydrolysis (7 days) reduces X_c by breaking long molecular chains into shorter glucose ones, reducing SNC yield. Melting temperatures (Tp) of pretreated SNC increase after 5 days of hydrolysis. Pretreated carioca bean starch shows advantages for SNC production after 5 days of hydrolysis, reaching good yield and X_c. HMT and SNT prove effective in improving hydrolysis yield and thermal stability, while ANN slightly accelerates SNC production. Their findings provide valuable insights into optimizing pretreatments for enhancing SNC properties and expanding their applications.