Mountainside, NJ real estate: the numbers, explained.

Home values in Mountainside

Zillow Home Value Index (all homes, middle tier, smoothed, seasonally adjusted) for the Zillow region “Mountainside”, September 30 of each year. Source: Zillow Research.

Zillow’s Home Value Index for Mountainside was $1,050,443 as of September 30, 2026, up 3.8% from a year earlier and up 33.7% over five years. Over ten years the index rose 54.4%. ZHVI models a typical home value. It isn’t the price of any specific house.

The NJ Division of Taxation’s 2026 Average Residential Statistics show an average residential sale price of $942,866 across 29 sales used in that report. Averages can be pulled up or down by a few sales, which is one reason it can differ from Zillow’s index.

The Census Bureau’s survey puts the median value of owner-occupied homes, as estimated by owners, at $810,300 (2020–2024 average), compared with a Union County town median of $533,300.

Mountainside property taxes

Mountainside’s 2025 general tax rate was 2.1 per $100 of assessed value, and its effective tax rate was 1.566%, lower than the Union County town median of 2.113% and lower than the statewide municipal median of 2.141%. That ranks it #2 lowest of 21 Union County municipalities by effective rate. The average residential tax bill was $13,309 on an average assessment of $633,778 across 2,493 residential properties.

Applied to the typical home value of $1,050,443, the effective rate implies roughly $16,450 a year ($1,371 a month) in property tax. The Division publishes the effective rate for comparing towns, not for computing a specific bill, so use it as a ballpark.

What it costs to own vs. rent

For a $1,050,443 home with 20% down ($210,089) and a 30-year fixed loan at 7.18%, Freddie Mac’s national average for the week of November 5, 2026, principal and interest come to about $5,693 a month. With estimated property tax that’s about $7,064, before insurance, any HOA fee and utilities. For comparison, the Census median gross rent in Mountainside is $3,501.

Run my numbers for MountainsideRent vs buy here

Who lives in Mountainside

About 7,049 people live in Mountainside. 87.9% of occupied homes are owner-occupied (county town median 68.3%), so the market is mostly owner-occupied single homes. 97.2% of housing units are single-family detached houses. The median resident age is 48, and 67.3% of adults 25 and older hold a bachelor’s degree or higher. Median household income is $211,538, higher than the county town median of $119,464.

The median home in Mountainside was built in 1957. Much of the housing predates 1978, so buyers should plan for older-home checks: lead-based paint disclosure, an oil-tank sweep if the house ever had oil heat, knob-and-tube or older electrical, galvanized plumbing, and a sewer-line scope. See the NJ inspection checklist.

Commuting from Mountainside

Workers in Mountainside average 36 minutes each way (those who don’t work from home), longer than the Union County town median of 31.5 minutes. 8.1% commute by public transportation, so transit is a real option for some commuters and 25.1% work from home.

Schools

I don’t republish unofficial school scores. For Mountainside, start with the New Jersey Department of Education’s School Performance Reports, then confirm the exact school assignment for any address with the district, since some NJ towns send students to regional or neighboring high schools. See how to research NJ schools.

Downtown, food and things to do

The best way to judge Mountainside’s restaurants, parks and weekend life is in person. Visit on a weeknight and a Saturday morning, check the town recreation calendar and walk the blocks you’d live on. My town scouting checklist shows what to look for.

My take for buyers, sellers and renters

• Buyers: a below-county-median effective tax rate stretches your budget further here than in many Union towns. Compare with the town comparison tool.
• Sellers: values are up 33.7% in five years, so many owners have significant equity. See your number in the seller net sheet.
• Low turnover: about 29 residential sales were in the state’s 2026 report, so good listings can be scarce. Set alerts and be ready to act.

Nearby towns at a similar price