Previous associations have been observed not only between risk factors and falls but also between falls and their clinical outcomes based on some cross-sectional designs, but their causal associations were still largely unclear. We performed Mendelian randomization (MR), multivariate Mendelian randomization (MVMR), and mediation analyses to explore the effects of falls. Our study data are mainly based on White European individuals (40–69 years) downloaded from the UK Biobank. MR analyses showed that osteoporosis (p= 0.006), BMI (p= 0.003), sleeplessness (p< 0.001), rheumatoid arthritis (p= 0.001), waist circumference (p< 0.001), and hip circumference (p< 0.001) have causal effects on falls. In addition, for every one standard deviation increase in fall risk, the risk of fracture increased by 1.148 (p< 0.001), the risk of stroke increased by 2.908 (p= 0.003), and a 1.016-fold risk increase in epilepsy (p= 0.009). The MVMR found that sleeplessness is an important risk factor for falls. Finally, our mediation analyses estimated the mediation effects of falls on the hip circumference and fracture (p< 0.001), waist circumference and epilepsy (p< 0.001), and sleeplessness and fracture (p= 0.005). Our study inferred the causal effects between risk factors and falls, falls, and outcomes, and also constructed three causal chains from risk factors → falls → falls outcomes.