Promotion of positive experiences in companion animals is essential for maximising good welfare. However, the dearth of published literature on the experience and expression of positive emotional states in companion dogs suggests they are less well understood than negative emotions. Owner knowledge can provide a basis for generating hypotheses for experimental research, and can inform education initiatives. An online survey of 445 dog (Canis familiaris) owners in the United Kingdom and the Republic of Ireland was used to identify key contexts and behaviours perceived by owners to be associated with positive emotions for companion dogs, and to examine factors which influence owner reports of key behaviours. The contexts most commonly associated with positive high arousal (PHA; ‘happy and excited’) were anticipation of walks or food and with positive low arousal (PLA; ‘happy and relaxed’) were resting and gentle stroking. Respondents’ behavioural profile for canine PHA involved barking, head held high, wide open and ‘bright’ eyes, ears pricked, tail wagging, mouth open, and active, playful behaviour. For PLA, respondents collectively described their dogs as silent, head resting, eyes closed or slightly closed, ears ‘down’, mouth closed and a calm/relaxed activity level. Notably, PLA states were described in less detail than PHA, suggesting the former may be less well understood or difficult to interpret. Dog breed and age, and owner experience and level of attachment to their pet significantly influenced respondents’ likelihood to report certain behavioural indicators, and may influence assessments of pet behaviour and underlying emotion. Further work is required to determine the validity of the behavioural expression and contexts perceived to be associated with positive experiences in dogs.