There is a lack of empirical studies on the interplay between attachment pattern, emotion regulation, and loneliness. This is surprising considering the extensive theoretical background on these three constructs, and the adverse adult life outcomes associated with insecure attachment, emotion regulation deficits, and loneliness. The present study investigated how attachment style and emotion regulation deficits are each related to loneliness. The study expected that higher levels of anxious and avoidant attachment will be associated with higher levels of loneliness (H1), and higher emotion regulation deficits will be associated with greater loneliness (H2). In addition, for an exploratory purpose, the study also assessed the moderating role of emotion regulation in the relationship between attachment and loneliness. Data from a total of 215 participants (aged 19-70) were collected via an online survey assessing attachment patterns, emotion regulation deficits, and levels of loneliness. Three multiple linear regression analyses were performed with results indicating that insecure attachment may be positively associated with loneliness, and that attachment anxiety may have a stronger positive association with loneliness as compared to attachment avoidance. Furthermore, the current findings suggest that higher emotion regulation deficits may also be positively associated with loneliness. However, the results of the exploratory analysis assessing the interaction of emotion regulation deficits in the relationship between attachment and loneliness suggest that emotion regulation may not act as a moderator. The current study contributes to research aiming to develop a better understanding of the factors that may be related to subjective feelings of loneliness.