Commonly observed low activity of older adults harms their well-being. We perceive the retirement as a new opening that could be utilized to fulfill previously neglected needs and involve in new activities. They can be a remedy for losing the sense of life while changing the social role and getting older. This study explores trends in activity over retirement. In particular, it verifies if different post-retirement activities: 1) formal social engagement; 2) informal help given outside the household; 3) solitary leisure or self-development activities, and 4) sociable leisure or self-development activities are mutually exclusive or supportive of each other. We use the data from 4 and 6th wave of Survey of Health, Ageing and Retirement in Europe, taking into consideration 2757 respondents who participated in both waves. We analyze trends in activity over retirement and verify the hypotheses regarding the relationships between engaging into different types of activities and between the activity and development of personal social networks. We conduct the descriptive analysis and utilize the Generalized Structural Equation Model. Most people do not change their involvement in different activities after retirement. Among those who change, the average trend is upward. We find support that different types of activities undertaken after retirement do not crowd out each other. On the contrary, being active in one sphere goes hand in hand with activity in another. We give evidence for presence of social network mechanisms that enhance such understood complementarity. Maintaining social relationships correlates with engagement in socially-oriented activities and privately-oriented sociable pastimes. Being active, with exception of solitary forms of recreation, creates an opportunity to foster relations with other people and, thanks to their encouragement, to engage in new activities. The small change in activity after retirement signifies the need to encourage non-work activity during earlier stages of life. As different types of post-retirement activities are complementary, the most active group of older adults would be the most open for social engagement and volunteering, however the least active group needs the biggest support to involve in any activities.