As part of a program of research to develop and evaluate assessments of interpersonal skills, we developed a dyadic negotiation task that allows participants to select options and to communicate with each other through a chat window interface. Based on the New Recruit negotiation task, we developed an assessment of negotiation skills that included three negotiation issue types—distributive (zero-sum), integrative (trade-off), and compatible (aligned)--implemented in two tasks (Fundraiser and Robot) given to 84 participants in dyads. We found evidence for the generalizability of negotiation skill across tasks at both the individual (r = 0.62) and joint (r = 0.74) levels. Participants' chat turns were coded into 14 tactic categories (e.g., making a concession, stating a disagreement). Tactic use across tasks was consistent at both individual (average correlation was r = 0.52), and joint (r = 0.58) levels. Principal component analysis of tactics used identified four tactic types (cooperative, competitive, greetings, impasse). Greater use of cooperative tactics was associated with higher joint negotiation scores (i.e., sum of individual scores). This research contributes to an understanding of negotiation as a general individual and joint skill and suggests specific tactics associated with that skill. The research also highlights the value of an online platform for conducting such research that enables small-group interactive task performance in which participants communicate with each other using a text-based chat box.