Limited socialisation can contribute to the development of undesirable dog behaviours. The COVID-19 lockdown potentially limited socialisation opportunities, which may negatively impact the future behaviour of puppies raised during lockdown. Data were gathered from longitudinal study participants in the United Kingdom/Republic of Ireland via multiple questionnaires between May 2016 and November 2022. The impact of age and lockdown phase (pre-, during, and post-) on the types of socialisation experiences of 8-to-19-week-old puppies and the recency of socialisation experiences of approximately 6-month-old puppies were examined. Puppies under 19-weeks had significantly more types of socialisation experiences (from a predefined list) as they aged, and pre-lockdown compared to post-lockdown, but not between other lockdown phases. Most 6-month-old puppies had met a new adult or dog outside the household, a familiar dog, and/or a child within the last 1-7 days, and this was similar between lockdown phases. During lockdown, 6-month-old puppies experienced longer periods between meeting a new adult in their home. Puppies were hypothesised to have had fewer experiences during lockdown, but this was not found. However, the quantity and quality of these experiences may have been affected. Future research within this longitudinal study will explore relationships between the timing and type of experiences had by puppies and their subsequent behaviour.