Children with twice-exceptionality (2e) who combine Autism Spectrum Disorder (ASD) and high intellectual ability represent an under-researched and highly complex population, both in terms of assessment and intervention. This study describes the developmental trajectory of a 2e child identified at 27 months and evaluates the feasibility and effects of a combined package of Naturalistic Developmental Behavioral Interventions (NDBI) plus giftedness enrichment. The objective was to longitudinally characterize the child's cognitive, socio-emotional, and adaptive profile, and to estimate changes in social communication, engagement in high-challenge tasks, and daily functioning, using a single-case design with three annual assessment points (T1-T2-T3). A multiple-baseline design across contexts and target behaviors was employed. The intervention included natural environment teaching, motivational reinforcement, curriculum compacting, and progressive cognitive challenges, in addition to caregiver and teacher training. Dose: one 60-minute weekly session plus daily home practice. Primary measures were functional communicative acts, joint attention, active participation, and problem behaviors; the assessment points also included standardized scales (ASD, development/cognition, adaptation). Results: At T1, the child was diagnosed with ASD requiring level 2 support and was minimally verbal; cognitive performance was equivalent to 30 months. At T2, the support level remained at 2, with cognitive performance increasing to 54 months. At T3, the child presented ASD requiring level 1 support, with verbal language, and a discrepant WPPSI-III profile (Verbal IQ = 94, Performance IQ = 122, Full-Scale IQ = 107; Language = 126). Session and assessment data integration suggests improvements in communication and participation, with generalization across contexts. The combination of NDBI and enrichment appears to enhance engagement by aligning intense interests with higher-complexity demands, thereby fostering meaningful practice opportunities and natural reinforcement. Implications are discussed for individualized educational planning and home-school-clinic collaboration.