Participation in triadic medical interaction can be more unpredictable and challenging than that in dyadic interactions limited to patients and physicians. Many studies have explored participants' roles or communication strategies in triadic medical interaction but seldom investigated discursive resources and actions of the third party in interactional tension, especially in Chinese healthcare settings. Eighty-two conversations involving 45 patients, 57 companions, and four physicians were audio-recorded at the neurology clinic of a tertiary hospital in northern China, each lasting between 12 and 20 min. Through conversation analysis, the moments and activities that the third party intervenes in the interactional tension are captured and analyzed at a micro-level. Our collected data reveal that the third-party intervention can be classified into double, unilateral, and nonaligned. Along the gradient, initiatives for actions by the third party are diminished. Five distinct behavioral patterns are identified to represent alignment choices, including serving as and beyond a sounding board, downgrading one side to keep the stance back, prioritizing one party, and deflecting with non-verbal cues and fact-based formulation. This study sheds light on the practical implications of alleviating and addressing the emerging tension before it spreads, especially in neurology clinics where companions are frequently involved. When tension-related parties are at an impasse, the third party can step in by seizing the opportune moment and act as a gatekeeper for the spill-over of the tension through the design and organization of sequences in the interaction.