||Purpose: The effect of bilingual service delivery on treatment of speech sound disorders (SSDs) in bilingual children is largely unknown. Bilingual children with SSDs are typically provided intervention in only one language, although research suggests dual-language instruction for language disorders is best practice for bilinguals. This study examined cross-linguistic generalization of bilingual intervention in treatment of two 5-year-old sequential bilingual boys with SSDs (one with Childhood Apraxia of Speech), hypothesizing that selecting and treating targets in both languages would result in significant overall change in their English and Spanish speech systems. Method: A multiple baseline across behaviours design was used to measure treatment effectiveness for two targets per child. Children received treatment 2–3 times per week for 8 weeks and in Spanish for at least 2 of every 3 days. Ongoing treatment performance was measured in probes in both languages; overall speech skills were compared pre- and post-treatment. Result: Both children's speech improved in both languages with similar magnitude; there was improvement in some non-treated errors. Conclusion:Treating both languages had an overall positive effect on these bilingual children's speech. Future bilingual intervention research should explore alternating treatments designs, efficiency of monolingual vs bilingual treatment, different language and bilingual backgrounds, and between-group comparisons.