<p>Although inclusive local participation in climate adaptation is touted as the panacea to ensure that project outcomes serve the needs of the most vulnerable, there is no objective measure for group inclusiveness. This study departs from the existing psycho-affective scales and employs principal factor analysis to compute a communicative practice-based inclusiveness scale (CoP-BIS). CoP-BIS measures group inclusiveness with five indicators—ideas solicitation, acknowledgment of views, views utilization, feedback provision, and member involvement. Ordinary least squares analytical procedure is applied to estimate the association between group inclusiveness and group members' participation in decision making, based on data from a survey with 225 respondents randomly sampled from farmers' and fishers' groups in Ghana's Effutu Municipality. We found that group inclusiveness has a statistically significant positive association with all three dimensions of participation (feeling encouraged to participate, <i>willingness</i> to make efforts to participate, and actual participation) inadaptation decision making at the 1% alpha level when other relevant factors are controlled for. Thus, fostering group inclusiveness through inclusive communicative practices is critical in promoting diverse participation in adaptation decision making. The implications for policy and practice are discussed.</p>