More than 100 officers using dogs and helicopters searched woods near the town of Doorn but failed to find any trace of the youngsters, DutchNews.nl reported.
The brothers, ages 7 and 9, disappeared while spending the day with their father, police said.
The father committed suicide in the woods Tuesday morning, the news website said. He had been seen filling up his car with gas Monday night in the town of Limburg.
Police in Germany, Belgium and Luxembourg have been alerted about the boys' disappearance.
Iris van der Schuit, the boys' mother, posted on Facebook that she is "going mad" over lack of news about her sons.