Kalshi Just Had Its Biggest Week Ever — $3.4 Billion, and Sports Drove 88% of It

The week ending April 26 produced a number that the prediction market industry has been building toward for months. Kalshi processed $3.4 billion in notional trading volume — a new all-time weekly high for the platform — according to data from Artemis. But the more telling figure is buried inside that headline number: sports markets alone accounted for $3 billion, or 88 percent of Kalshi’s total weekly volume. That single category generated more trading activity than Polymarket’s entire platform for the same week.

Sports Is Now Driving the Platform

The NBA playoffs were the primary engine behind the surge. Kalshi has been building out its sports market infrastructure since launching sports event contracts in January 2025, and the growth has been rapid by almost any measure. The platform now describes itself as the first nationwide legal sports betting app, operating under CFTC oversight rather than state gaming licenses. For the week ending April 26, sports volume hit a new all-time high of its own — $3 billion — with crypto markets a distant second at $334.1 million and politics generating just $16.8 million, less than half a percent of total volume.

Polymarket’s composition during the same period was starkly different. The decentralized platform recorded roughly $2 billion in total weekly volume, with sports accounting for $959.1 million, politics at $507.3 million, and crypto generating around $416 million. The contrast illustrates how differently the two leading prediction market platforms have developed. Kalshi is running close to 90 percent sports at peak moments. Polymarket is a more diversified platform where politics and crypto together often rival sports volume.

What This Milestone Actually Means

For bettors, the data points to something important about where prediction markets are headed. Kalshi’s sports volume growth has tracked closely with the sports calendar. The platform set prior weekly volume records during NFL playoff weeks and March Madness, then cleared those benchmarks again during the Masters — which generated $545 million in trading on Kalshi alone, making it the single largest sports event in the platform’s history at the time. The April 26 week, driven by the NBA playoffs, pushed the ceiling even higher.

The practical implication is that prediction markets are no longer a niche product for political traders or crypto-adjacent speculators. They are increasingly functioning as a parallel sports betting market, and one that operates in all 50 states regardless of whether individual states have legalized traditional sports betting. That is the core source of tension between Kalshi and state regulators. Eleven states have issued cease-and-desist orders or initiated enforcement actions against the platform, arguing that sports event contracts constitute illegal gambling under state law.

The Sportsbook vs. Prediction Market Line Is Blurring

Traditional sportsbooks and prediction market operators are increasingly competing for the same customers. The product structures differ — sportsbook bets resolve against a house or other bettors via fixed odds, while prediction market contracts trade as binary options on an exchange — but the underlying activity, wagering on sports outcomes, is largely the same from a consumer perspective.

That convergence is why the current legal and regulatory environment matters so much to anyone who bets on sports. The outcome of Kalshi’s ongoing litigation against multiple state gaming regulators will help determine whether prediction markets can continue operating freely or whether their footprint gets constrained to states with favorable regulatory postures. With $3 billion in a single week now on the board for sports alone, the economic stakes on both sides of that fight have never been higher. If you are shopping for sportsbook promotions and wondering why some sites look different than others, this is part of the reason — the market structure itself is in flux.