Short answer: Yes—often. A heavy-duty work vest can replace a jacket in many mild-weather situations, but whether it’s a good substitute depends on temperature, wind, precipitation, activity level, and what you need from outerwear (warmth, protection, pockets, visibility).

What a vest does well

• Keeps core warm while leaving arms free—good for physically active work (lifting, tool use, driving, climbing ladders).
• Better mobility and less bulk than a jacket.
• Heavy-duty vests often have tough outer fabrics, reinforced panels, and lots of pockets for tools and gear.
• If it’s insulated (down, synthetic, or heavy fleece), it can provide significant warmth for mild conditions.

When a vest is a good replacement

• Mild temperatures where you primarily need core warmth but don’t need full-arm protection (roughly the 45–65°F / 7–18°C range for many people, though this varies by personal tolerance and wind).
• Low-to-moderate wind and little risk of rain.
• Active work where you want arm freedom (carpentry, landscaping, warehouse work).

Limitations compared with a jacket

• Arms are exposed—less warmth in colder or windier conditions.
• Less protection from rain/snow unless the vest has a waterproof shell.
• Doesn’t replace features like a hood, full sleeve insulation, or cuff seals to keep out drafts.
• If you need full-body protection from chemicals, chainsaw chaps, or heavy weather, a jacket (or specialized outerwear) is necessary.

Practical tips for replacing a jacket with a vest

• Layer smart: wear a moisture-wicking base layer and a long-sleeve midlayer (flannel, thermal, or lightweight fleece) under the vest. Add or remove layers as your activity or temperature changes.
• Choose the right vest: insulated for cooler mild days; softshell for wind resistance; waterproof/breathable shell vests if you need light rain protection.
• Look for features you need: reinforced shoulders, tool pockets, breathable vents, high-visibility panels if required by your job.
• Carry a lightweight packable jacket if conditions might turn cold, windy, or wet—vest + packable shell is a versatile combo.
• Fit: the vest should sit comfortably over layers without restricting movement; longer tails help keep drafts out.

When not to rely on a vest

• Cold, windy, or wet weather where arm coverage, a hood, or sealed cuffs matter.
• When you’ll be stationary for long periods (vests keep moving workers warmer than those standing still).
• Work requiring full-sleeve protective materials (chemical, flame, chainsaw-rated clothing, etc.).

Bottom line: For many mild-weather, active work scenarios, a heavy-duty work vest is a practical and often superior alternative to a jacket—provided you choose the right type of vest and layer appropriately. If you expect wind, rain, or prolonged exposure while stationary, keep a jacket available.