About
Flats on First is a luxury apartment community in East Cambridge at 21 Charles Street. Floor plans span studios through three-bedroom layouts, with sizes ranging from 439 to 1,303 square feet. Inside, homes include gourmet kitchens with stainless steel appliances, quartz countertops, designer custom cabinetry with ceramic and glass tile backsplash, wood-grained vinyl flooring, full-size high-efficiency washers and dryers, and Schlage smart locks. Around the community, you’ll find a roof deck with city views, a 24-hour fitness center, outdoor lounges with fire pits, a 24-hour package room, co-working spaces, and a controlled-access parking garage. The location makes it easy to get around: Kendall/MIT Station (MBTA Red Line) and Lechmere (MBTA Green Line) are nearby, with quick access to the Charles River and Memorial Drive.
Rent by bedroom
| Home | Starting rent | Floor plans |
|---|---|---|
 Studio439–627 sq ft |
From $3,967/mo | 4 |
 1 Bedroom699–1,101 sq ft |
From $3,967/mo | 10 |
 2 Bedroom909–1,221 sq ft |
From $3,967/mo | 8 |
 3 Bedroom1,303 sq ft |
From $6,629/mo | 1 |
Floor Plans
23 floor plans · 439–1,303 sq ft.
Current availability is not tracked for this community. Contact the property or visit the official property website for available homes. Floor-plan details describe the community and do not indicate current unit availability.
Studios
4 plans · 439–627 sq ft
1 Bedroom
10 plans · 699–1,101 sq ft
2 Bedroom
8 plans · 909–1,221 sq ft
3+ Bedroom
1 plan · 1,303 sq ftCosts & fees
These are the charges we have confirmed. They may not be the full list, so no total monthly price is shown — confirm all charges directly with the property.
Charges that apply in some circumstances
Refundable deposits
Pets & Parking
Leasing Policies
Community Amenities
- 24-hour fitness center
- 24-hour package room
- Bike rack
- Bike storage
- ButterflyMX intercom system
- Co-working spaces
- Community kitchen and dining
- Community lounge
- Community lounge & kitchen
- Controlled access parking garage
- Game room
- Grilling and al fresco dining
- Groom room
- Landscaped courtyards with outdoor seating
- Leasing office
- Open air amphitheater
- Outdoor firepit & lounge
- Outdoor lounges with fire pits
- Roof deck grill & lounge
- Roof deck with city views
- Social spaces with complimentary WiFi
Unit Features
Neighborhood
What Sets Flats on First Apart
Photos
1 photos.
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Property FAQs
What floor plans are available at Flats on First?
What is the apartment size range?
What are some in-home features in the apartments?
What community amenities are available?
What are the leasing office hours?
How do I contact the leasing office?
What transit options are near Flats on First?
Common rental questions about Flats on First
Illustrative examples answered from the property's published details — not a record of questions renters have asked, and not a guarantee.
Apartments in East Cambridge near Kendall/MIT Station or Lechmere — what should I look at?
Flats on First is in East Cambridge at 21 Charles Street, with quick access to Kendall/MIT Station (MBTA Red Line) and Lechmere (MBTA Green Line). Floor plans run from studios (439–627 sq ft) up to a 3-bedroom, 2-bath (1,303 sq ft). You’ll also find co-working spaces, a 24-hour fitness center, and a 24-hour package room.
What apartments in Cambridge have a roof deck with city views and co-working spaces?
Flats on First in East Cambridge has a roof deck with city views, plus a roof deck grill & lounge. Work-from-home setups are covered with co-working spaces and social areas with complimentary WiFi. Units include full-size high-efficiency washers/dryers, stainless steel appliances, and quartz countertops.
I want an apartment with garage parking and smart locks in Cambridge, MA — any options?
Flats on First at 21 Charles Street in Cambridge has a controlled access parking garage and Schlage smart locks. Apartments range from studios to 3-bedroom layouts, and many homes include balconies and walk-in closets. Controlled-access features like a ButterflyMX intercom system are on-site too.