Is the word agenda the same in Brazilian and European Portuguese?

No

While the spelling, grammar, and the definition of "agenda" as a physical or digital planner are identical in both variants, there is a difference in typical usage.

In Brazil, "agenda" is used broadly to refer to a person's entire schedule, their availability, or the list of topics for a meeting. In Portugal, while "agenda" is used for the physical object, a person is more likely to use "ordem do dia" to refer to a meeting's agenda, and "horário" (timetable/fixed schedule) or "compromissos" (appointments/commitments) to refer to their personal schedule or availability.

Brazilian Portuguese Examples

1. "Esqueci de anotar o número na minha agenda." (I forgot to write the number in my planner.)
2. "A agenda da reunião de hoje está muito extensa." (Today's meeting agenda is very long.)
3. "Minha agenda está muito lotada esta semana." (My schedule is very full this week.)
4. "Vou conferir minha agenda e te aviso se posso ir." (I'll check my schedule and let you know if I can go.)
5. "Ele organizou todos os seus compromissos na agenda." (He organized all his appointments in his planner.)

Continental Portuguese Examples

1. "Esqueci de anotar o número na minha agenda." (I forgot to write the number in my planner.)
2. "Qual é a ordem do dia para a reunião?" (What is the agenda for the meeting?)
3. "Tenho muitos compromissos esta semana." (I have many appointments/commitments this week.)
4. "Vou ver o meu horário e aviso-te se posso ir." (I'll check my schedule and let you know if I can go.)
5. "Ele organizou todos os seus compromissos na agenda." (He organized all his appointments in his planner.)