2018–19 United Counties League Division One

At the end of the 2017–18 season, the following teams left the division:
 * Promoted to Step 5
 * Pinchbeck United, to the Premier Division
 * Potton United
 * Transferred within Step 6
 * Buckingham Town, to the Spartan South Midlands League
 * Relegated to Step 7
 * Oakham United
 * Stewarts & Lloyds Corby
 * Closed at the end of the season
 * Olney Town

The remaining 14 teams, together with the following, form Division One for season 2018–19:
 * Relegated from Step 5
 * Northampton Sileby Rangers, from the Premier Division
 * St Andrews, from the Premier Division
 * Transferred within Step 6
 * Anstey Nomads, from the East Midlands Counties League
 * Aylestone Park, from the East Midlands Counties League
 * Birstall United, from the East Midlands Counties League
 * Holwell Sports, from the East Midlands Counties League