The aims of this study were to analyze whether positive and negative affect, social support, and loneliness are factors longitudinally related to suicide ideation in the general population in different age groups. A total of 2,392 individuals from a nationally representative sample of the Spanish general population were evaluated in 2011–2012 and in 2014–2015. After including relevant control variables in the analyses, lower positive affect was prospectively related to ideation in 18- to 59-year-old individuals, whereas feelings of loneliness were related to ideation in 60-year-and-older individuals. Social support was not associated with suicide ideation in any age group. These results are in line with the need for age-tailored suicide prevention programs. The present findings might also suggest that health care professionals should consider feelings of loneliness rather than social support to assess the presence of suicide ideation in older people.