Short answer. Yes. Although an illegitimate child ordinarily carries the mother's surname, the law allows the child to use the father's surname if the father has expressly recognized the child in the birth record, or in a public document or a private handwritten instrument signed by the father.
What the law says
illegitimate children may use the surname of their father if their filiation has been expressly recognized by the father through the record of birth appearing in the civil register, or when an admission in a public document or private handwritten instrument is made by the father
RA 9255, Section 1 — Surname Of Illegitimate Children. Read the full provision →
The default, and the exception
The starting rule is that an illegitimate child uses the mother's surname and is under her parental authority. But the law opens a clear path to the father's surname when he acknowledges the child. It provides that illegitimate children may use the surname of their father if their filiation has been expressly recognized by the father through the record of birth appearing in the civil register, or when an admission in a public document or private handwritten instrument is made by the father. The key is genuine recognition by the father. Where that exists, using his surname becomes an option — a right the child may exercise, not something forced either way.
What counts as recognition
The law names specific forms of acknowledgment, and they matter. Recognition can appear in the child's record of birth in the civil register — the father's acknowledged entry there. It can also come through an admission in a public document, or in a private handwritten instrument made by the father. What ties these together is that the father himself must have expressly recognised the child in one of these ways. Casual references, or a mother's say-so, are not the same thing. The surname right rests on the father's own recognised act, set down in the kind of record the law will accept.
The father's continuing role
Recognition is not a trap that strips the father of any later voice. The law preserves his right to institute an action before the regular courts to prove non-filiation during his lifetime. That is a safeguard against false claims of fatherhood — the recognised father can go to court to contest paternity if he maintains the child is not his. On the other side, acknowledgment carries responsibilities as well as a surname, since a recognised illegitimate child is entitled to support and, on the inheritance side, to a legitime equal to one-half of that of a legitimate child.
Putting it into effect
Because the surname right depends on a valid act of recognition, the practical work is making sure that act is properly documented — the father's acknowledgment on the birth record, or a proper public document or handwritten instrument he executed. If recognition exists but the birth record does not yet reflect the father's surname, changing it involves following the correct civil-registry procedure rather than simply writing a new name on forms. Because the requirements are specific and mistakes can stall the process, it helps to confirm with the local civil registrar or a lawyer exactly what document is needed and how the record is updated.