The shocking graffiti includes swastikas and references to white supremacy and far-right political movements.
The vandalism is understood to have occurred overnight, on the outside walls of Heron Foods, Age UK, and the hearing centre.
The police have been informed about the incidents.
Nancy Shackleton, who took these photographs of the graffiti, was one of many local residents to express their disgust on the Horncastle Community Page on Facebook, and elsewhere on social media.
Nancy told the News: “I was disgusted and disappointed to see that in our town. I very much hope this is just an isolated incident.
“Also, strange behaviour for someone to spray paint support for far-right groups and then spell Britain wrong!”
This afternoon, a Lincolnshire Police spokesman confirmed: “(This incident was) reported to us at 9.10 this morning were numerous incidents of graffiti that had appeared overnight in Horncastle.
“We have been conducting house to house enquiries and assessing CCTV opportunities.
“We will be upping our patrols in the area especially during hours of darkness.
“We are determined to find out who did this and we are urging the community to help by giving us any information that could relate to this mindless criminal damage.”
The police spokesman added that, due to the language used, the incident would be treated as a hate crime.
If you have any information, contact Lincolnshire Police on 101, quoting reference number 80 of June 28.
Horncastle Town Council has been contacted for comment.