The association between loneliness and suicidality has been documented in many studies, but these studies have been limited by cross-sectional designs and the use of adult-only populations. The purpose of the current study was to overcome these limitations by (a) investigating whether the link between loneliness and suicidal thoughts and behaviors occurs cross-sectionally, longitudinally, or both and (b) investigating how the link between loneliness and suicidality might be influenced by different demographic variables, including gender, ethnicity, and socioeconomic status. Logistic regression analyses were used to analyze data from a large sample (N = 937) of youth from the NICHD Study of Early Child Care. Results indicated that loneliness at age 15 years was concurrently associated with both suicidal ideation and suicidal behavior at age 15 years. Loneliness in middle childhood was longitudinally associated with suicidal behaviors at age 15 years, but not with suicidal ideation at age 15 years. None of the demographic characteristics influenced these associations.