This paper examines the intervention behavior of small or middle-sized neighbor countries in civil war peace negotiations by examining Thailand in the Cambodian peace process and Chad in the peace negotiations over Darfur, Sudan. Firstly, it presents that the primary motivations for the interventions were two types of fear: fear of the potentially critical domestic impact of the external conflicts, and fear of their limited leverage over the conflicts. Secondly, these states pursued proactive but biased strategies for early intervention, which included providing physical/substantial support to one side in the conflicts, submitting unilateral peace proposals, and attempting to strengthen their diplomatic alliances. Thirdly, while both countries changed their intervention strategies in an effort to assume a more constructive role in the respective peace processes, the consequences of their changed strategies differed fundamentally, a difference chiefly due to how their new diplomatic strategies were utilized and supported by external actors.