Taking the bad with the good is a necessity of life, and people who readily integrate thoughts of their loved one’s flaws with thoughts of their more positive attributes maintain more stable, satisfying relationships. Borderline personality disorder, however, is often characterized by interpersonal perceptions that fluctuate between extremes of good and bad. We used a timed judgment task to examine information processing about significant others in individuals high in borderline personality features relative to healthy individuals and those high in avoidant personality features. In Study 1, when judging traits of a liked significant other, same-valence facilitation by negative primes (judging negative traits faster than positive traits after a negative prime) was significantly stronger in the borderline features group than the other two groups, and was inversely associated with self-reports of integrated thoughts about significant others. In contrast, same-valence facilitation by positive primes (judging positive traits faster than negative traits after a positive prime) was significantly stronger in the avoidant features group than the other two groups, and inversely associated with self-esteem. No between-group differences in same-valence facilitation were statistically significant when participants judged traits of disliked significant others, liked foods, and disliked foods. In Study 2, same-valence facilitation by negative primes when judging traits of a liked significant other was significantly associated with less integrated positive/negative thoughts about that person in a 12-day diary. These results identify an implicit information-processing pattern relevant to interpersonal difficulties in borderline personality disorder.