Results showed that self-report means generally did not differ from informant-report means

From Self–Other Agreement in Personality Reports: A Meta-Analytic Comparison of Self- and Informant-Report Means by Hyunji Kim, Stefano I. Di Domenico, Brian S. Connelly.

From the Abstract:

Self-report questionnaires are the most commonly used personality assessment despite longstanding concerns that self-report responses may be distorted by self-protecting motives and response biases. In a large-scale meta-analysis (N = 33,033; k = 152 samples), we compared the means of self- and informant reports of the same target’s Big Five personality traits to examine the discrepancies in two rating sources and whether people see themselves more positively than they are seen by others. Inconsistent with a general self-enhancement effect, results showed that self-report means generally did not differ from informant-report means (average δ = −.038). Moderate mean differences were found only when we compared self-reports with stranger reports, suggesting that people are critical of unacquainted targets. We discuss implications of these findings for personality assessment and other fields in which self-enhancement motives are relevant.

Interesting on two counts. The belief that "self-report responses may be distorted by self-protecting motives and response biases" is a broad one and long-standing. Interesting that it might not be correct.

Interesting too, of course, that people are perhaps more accurate in their self-reflection than we have given credit for being.