Located on a premier residential street in the heart of Sherman Oaks, 4233 Costello Avenue is a masterfully designed modern residence that seamlessly pairs high-end privacy with an enviable, walkable lifestyle. Set behind imposing security gates and just steps from the area's premier restaurants, boutiques, and fitness studios, this 5-bedroom, 7-bathroom (5 full and 2 half) multi-level residence offers over 5,200 square feet of uncompromisingly luxurious living space. Beyond the architectural solid-wood pivot door, a light-filled formal living and dining area - defined by soaring ceilings, walls of glass, a custom glass wine enclosure, and the sculptural silhouette of a floating staircase-creates an exquisite atmosphere for sophisticated entertaining. Completing the front of the residence, a custom-tiled guest powder bath and a versatile main-floor en-suite bedroom - currently tailored as an office - feature a full bath and a private deck overlooking mature magnolia trees. At the rear of the home, an expansive kitchen and family great room center around a custom fireplace, an integrated surround sound system with an in-wall subwoofer, and Fleetwood glass sliders that open directly to the yard. The kitchen is curated for both function and scale, featuring a rare double island, a large walk-in pantry, extensive premium cabinetry, and a dramatic book-matched quartz accent above the stove. Complete with an elegant breakfast area, this space delivers a sense of volume and refined quality typically found in much higher-priced estates. Serving as the 1st of the home's 3 distinct levels, the lower level adds exceptional versatility, featuring a 2-car garage equipped with an EV charging station (complemented by 2 additional spaces in the driveway) finished with black epoxy floors and custom built-ins for showcasing your autos, along with a convenient half bath and a dedicated home theater. Climate-controlled by 2 HVAC systems that separate the top floor from the lower 2 levels, the upstairs features a wide, airy hallway connecting a laundry room to 4 independent en-suite bedrooms. Each suite features large picture windows with automated Shade Store shades and spa-like bathrooms with custom tilework and floating vanities. The primary suite serves as a secluded sanctuary, complete with high ceilings, a luxurious dual-sided fireplace shared between the bedroom and bath, a large walk-in closet, and an opulent porcelain bathroom featuring a soaking tub and an oversized frameless glass shower. Directly off the primary bedroom is one of the property's most distinctive features: a nearly 800-square-foot private, turfed terrace (not included in the official square footage), which is the perfect setting for a personal wellness retreat, with ample room for a sauna, cold plunge, and lounging area. From here, a private exterior staircase leads to the resort-caliber backyard, which includes a zero-edge infinity pool with a sun deck, and a manicured play area with a built-in BBQ. Designed for modern convenience, the entire estate operates as a fully integrated smart home, offering seamless WiFi control over the Nest thermostats, Ring and DVR home camera systems, Lutron lighting, pool, sprinklers, and localized Sonos speakers. Offering exceptional scale, bespoke amenities, and a coveted location, 4233 Costello Avenue stands out as a preeminent opportunity for luxury living in Sherman Oaks.