This study aimed at examining trends in magnesium intake among U.S. Hispanic adults stratified by gender, Hispanic origins, age, and poverty income ratio (PIR) level. Data on 9304 Hispanic adults aged ≥20 years from eight National Health and Nutrition Examination Survey (NHANES) cycles (1999–2014) were included in this study. For each cycle, survey-weighted mean dietary and total magnesium intakes were estimated. The prevalence of dietary and total magnesium intake below the Recommended Dietary Allowance (RDA) was further estimated stratified by gender and age groups. Linear regression was used to test trend. Over the survey cycles, both dietary and total magnesium intakes were significantly increased among Hispanic adults. In the study period, magnesium intake tended to be lower in females, adults in other Hispanic-origin group, those aged ≥65 years old, and those with a PIR <1.0. The prevalence of magnesium intake inadequacy decreased among Hispanic adults; however, more than 70% of Hispanic males and females continued to have magnesium intake below the RDA in 2013–2014. From 1999/2000 to 2013/2014, despite several improvements in magnesium intake having been identified, additional findings showed insufficient intake in Hispanic males and females, suggesting the need to improve magnesium intake through diet and dietary supplementation for U.S. Hispanics.