Objective: To evaluate the relationship between loneliness and cognitive functioning, and whether depressive and anxiety symptoms have intermediate roles therein. Methods: Information about 7,433 participants of the Irish Longitudinal Study on Ageing (a prospective, representative cohort study), aged over 50, was collected at three time-points two years apart, and analysed using Structural Equation Modelling to assess whether depressive and anxiety symptoms mediate the relationship between loneliness and cognitive functioning. Cognitive functioning was measured as a latent factor, with four indicators: measures of immediate and delayed word recall, verbal fluency, and a global measure (the MMSE). Loneliness was measured using the UCLA Loneliness scale, depressive symptoms using the CES-D-ML scale, and anxiety symptoms using the HADS-A scale. Results: Loneliness at time-point 1 predicted cognitive functioning at time-point 3, b ¼ �0.103, p<0.001, and depressive (b¼0.426, p<0.001) and anxiety (b¼0.410, p<0.001) symptoms at time-point 2. Depressive (b ¼ �0.020, p¼0.001) but not anxiety (b ¼ �0.000, p¼0.658) symptoms mediated the relationship between loneliness and cognitive functioning, total effect: b ¼ �0.123, p<0.001. Conclusion: The relationship between loneliness and cognitive functioning is in part explained by its relationship with depressive symptoms. Statistically, the mediation model helps us understand possible mechanisms through which loneliness impacts cognitive functioning. Results have implications for cognitive functioning interventions for older adults, and imply that loneliness is also a worthwhile target for intervention.