We aimed to evaluate which risk factors in middle-aged women are associated with higher risk of multimorbidity in older age. Study design: We conducted a prospective cohort study from 1990 to 1993 in Santiago de Chile, Chile among women aged 40-59 (at baseline). Diagnosed illnesses were retrieved from national health records in 2020. Main outcome measures: : Clinical and laboratory evaluation was conducted. Results: 1066 women were followed-up for a mean of 27.8 years, after which 49.7% presented multimorbidity. These women, as compared with those without multimorbidity, were more likely at baseline to have had obesity (20.4% vs. 8.6%, p < 0.001); be post-menopause (47.2% vs. 40.5%; p < 0.03); have jobs that did not require a qualification (74.2% vs. 56.0%, p < 0.001); arterial hypertension (19.8% vs 14.4%, p < 0.018); lower HDLcholesterol (51.3 ± 12.9 vs. 53.6 ± 12.7 mg/dL, p < 0.005); and higher triglyceride levels (136.0 ± 65.0 vs. 127.0 ± 74.0 mg/dL, p = 0.028). Hypertension was associated in 22.0% of women with diabetes, in 20.9% with osteoarthritis and 14.0% with depression. Osteoarthritis was also associated with diabetes mellitus (8.3%) and depression (7.8%). Diabetes mellitus, in addition to hypertension and osteoarthritis, was associated with depression (6.4%). In a logistic regression model, we observed that obesity in middle-aged women was the strongest risk factor for multimorbidity in the elderly (OR: 2.48; 95% CI, 1.71-3.61), followed by having a job that did not require a qualification (OR: 2.18; 95% CI, 1.67-2.83) and having a low HDL-cholesterol level (OR: 1.31; 95% CI, 1.02-1.68). Conclusions: Multimorbidity was highly prevalent in this older female population. Obesity in middle-aged women was the strongest risk factor for multimorbidity at older age. These results are relevant for Chile and other countries with similar population profiles.