Pesquisador vs. investigador
The difference between pesquisador and investigador is primarily regional. While both translate to "researcher", usage depends heavily on whether you are speaking Brazilian Portuguese or European Portuguese. In Brazil, the terms distinguish between scientific study and police work, whereas in Portugal, one term generally covers both roles.
Pesquisador
B1This is the standard term in Brazil for someone conducting academic, scientific, or market research. It implies searching for data, studying literature, or running experiments. In Portugal, this word is rarely used and can sound unnatural or specifically related to searching rather than studying.
O pesquisador publicou um artigo sobre mudanças climáticas.
(The researcher published an article about climate change.)
Ela trabalha como pesquisadora em um laboratório farmacêutico.
(She works as a researcher in a pharmaceutical laboratory.)
Os pesquisadores estão coletando dados para o censo.
(The researchers are collecting data for the census.)
Para ser um bom pesquisador, é preciso ter muita curiosidade acadêmica.
(To be a good researcher, one must have a lot of academic curiosity.)
Investigador
B1In Portugal, investigador is the universal word for a researcher, whether they work in a university, a science lab, or a police station. However, in Brazil, investigador is almost exclusively reserved for police detectives or private investigators looking into crimes and mysteries.
O investigador encontrou provas cruciais na cena do crime.
(The investigator found crucial evidence at the crime scene.)
Em Portugal, ele é um investigador renomado na área de biologia.
(In Portugal, he is a renowned researcher in the field of biology.)
A investigadora privada seguiu o suspeito por três dias.
(The private investigator followed the suspect for three days.)
O centro de estudos em Lisboa contratou um novo investigador principal.
(The study center in Lisbon hired a new lead researcher.)
Summary
To summarize, use pesquisador for academic/scientific contexts in Brazil. Use investigador for academic/scientific contexts in Portugal. Use investigador for police or detective work in both countries.