Two men, aged 28 and 33, were arrested at separate addresses in Daventry.
A 47-year-old man from Northampton and a 62-year-old man from Rockingham were also arrested.
All have been released under investigation.
The arrests were made as part of a week of intensified activity across the county by Northamptonshire Police’s paedophile online investigation team.
As well as the four arrests, eight children were safeguarded.
Det Insp Andy Rogers, who leads the team, said: “Anybody who thinks they are doing no wrong by downloading indecent images of children needs to think again.
“These are images of child abuse and downloading and sharing them not only perpetuates the abuse but facilitates further offending against victims.
“Those engaged in this activity need also to understand we have a team of experts dedicated to identifying them and bringing them to justice, so if they think they’ll go unnoticed, they’re very much mistaken.
“They can expect a knock at the door from a police officer with a warrant for their arrest, and from that moment on their whole lives and those of their families are likely to be turned upside down.
”In the past year, we’ve arrested 94 people for this type of offence.
“Suspects may be facilitating abuse from their home, but often children across the globe are affected, with devastating long-term implications for victims.”
If you have any information about a child at risk or about somebody downloading indecent images of children, call police on 101. Always call 999 in an emergency.
There is support available for anybody considering viewing indecent images of children, at www.stopitnow.org.uk or www.lucyfaithfull.org.uk.